Korean Journal of Chemical Engineering (v.30, #4)
Natural gas hydrate as a potential energy resource: From occurrence to production by Jiwoong Seol; Huen Lee (771-786).
Natural gas hydrate reservoirs have been strongly suggested as a potential energy resource. However, this potential is expected to be limited by geological factors, reservoir properties, and phase-equilibria considerations. Accordingly, sufficient understanding and accurate analyses for the complex surroundings in a natural gas hydrate system have to occur before methane recovery. In this paper, we discuss the formation and structure patterns of global natural gas hydrate, including the origins of hydrocarbon, crystal structures, and unique structure transition. We also summarize two important anomalies related to methane occupancy and chlorinity which were revealed very recently. Furthermore, we review the geological and chemical surroundings of the shallow hydrate deposits, the so-called brine patch discovered in the Cascadia Margin and Ulleung Basin, which are significantly related to tectonic conduits for methane gas and positive chlorinity.
Keywords: Natural Gas Hydrate; Methane Occupancy; Chlorinity; Shallow Hydrate; Ulleung Basin
Utilization of cane molasses for docosahexaenoic acid production by Schizochytrium sp. CCTCC M209059 by Lu-Jing Ren; Juan Li; Yuan-Wei Hu; Xiao-Jun Ji; He Huang (787-789).
Cane molasses (CM), an agro-industrial by-product, was first examined for docosahexaenoic acid (DHA) production by Schizochytrium sp. Cell dry weight as 21.94 g/L at treated CM cultivation was similar to that at pure glucose (26.7 g/L) cultivation. Batch fermentation at different initial CM concentration showed that DHA percentage could reach 47.51% at 10 g/L CM but only 37.90% at 70 g/L CM. By analyzing the fermentation process, monosodium glutamate might be a positive agent for effective DHA production. Finally, monosodium glutamate and malic acid were introduced to the fed-batch fermentation for effective DHA production.
Keywords: Docosahexaenoic Acid; Schizochytrium sp.; Cane Molasses; Lipid; Monosodium Glutamate
Temperature oscillations in methanol partial oxidation reactor for the production of hydrogen by Jinsu Kim; Jeonguk Byeon; Il Gyu Seo; Hyun Chan Lee; Dong Hyun Kim; Jietae Lee (790-795).
Methanol partial oxidation (POX) is a well-known reforming reaction for the production of hydrogen from methanol. Since POX is relatively fast and highly exothermic, this reforming method will be efficient for the fast startup and load-following operation. However, POX generates hot spots around catalyst and even oscillations in the reactor temperature. These should be relieved for longer operations of the reactor without catalyst degradations. For this, temperature oscillations in a POX reactor are investigated experimentally. Various patterns of temperature oscillations according to feed flow rates of reactants and reactor temperatures are obtained. The bifurcation phenomena from regular oscillations to chaotic oscillations are found as the methanol flow rate increases. These experimental results can be used for theoretical analyses of oscillations and for designing safe reforming reactors.
Keywords: Methanol Partial Oxidation; Temperature Oscillations; Chaotic Oscillations; Hydrogen Production
New emissions targeting strategy for site utility of process industries by Mohamamd Hasan Khoshgoftar Manesh; Sajad Khamis Abadi; Majid Amidpour; Hooman Ghalami; Mohammad Hosein Hamedi (796-812).
A new procedure for environmental targeting of co-generation system is presented. The proposed method is based on the concepts of pinch technology for total site targeting of fuel, power, steam, environmental impacts and total annualized cost with considering emissions taxes. This approach provides a consistent, general procedure for determining mass flow rates and efficiencies of the applied turbines. This algorithm utilizes the relationship of entropy with enthalpy and isentropic efficiency. Also, the life cycle assessment (LCA) as a well-known tool for analyzing environmental impacts on a wide perspective with reference to a product system and the related environmental and economic impacts have been applied. In this regard, a damage-oriented impact analysis method based on Eco-indicator 99 and footprints analysis was considered. In addition, the present work demonstrates the effect of including both sensible and latent heating of steam in the extended Site Utility Grand Composite Curve (ESUGCC). It is shown that including sensible heating allows for better thermal matching between the processes. Furthermore, the other representation YSUGCC as the other form of Site Utility Grand Composite has been proposed. Two case studies were used to illustrate the usefulness of the new environmental targeting method.
Keywords: Environemtal Targeting; Total Annulized Cost; Cogeneration; Total Site; New Procedure
Free convective flow over a vertical plate in a doubly stratified medium with electrophoresis, heat source/sink and chemical reaction effects by Periyanagounder Ganesan; Renugopal Kanniappan Suganthi (813-822).
We analyzed the problem of unsteady, incompressible free convective doubly stratified flow past a semiinfinite vertical plate with the influence of electrophoresis, heat source/sink and chemical reaction. The partial differential equations governing the flow are solved by employing an implicit finite difference scheme of Crank-Nicolson type. The effect of heat generation and absorption in stratified and unstratified flow are examined and hence the influence of stratification on velocity, temperature and concentration are investigated and presented graphically. Further, the impact of the electrophoresis on particle concentration in the presence of generative and destructive reaction is analyzed. As well, the effects of the physical parameters on local and average values of skin friction, Nusselt number and Sherwood number are also investigated and illustrated graphically. The particular solutions of the present results are compared with the existing solution in literature and are found to be in good agreement.
Keywords: Stratification; Electrophoresis; Heat Source; Heat Sink; Chemical Reaction
Viscous dissipation effect on heat transfer characteristics of mixed electromagnetic/pressure driven liquid flows inside micropumps by Mostafa Shojaeian; Seyyed Mohammad Nima Shojaee (823-830).
This paper presents the effect of viscous dissipation on heat transfer characteristics of mixed electromagnetic/ pressure driven liquid slip flows inside parallel plate microchannels. Flow is governed by the Navier-Stokes equations subject to the imposition of electromagnetic field with the boundary condition appropriate to the slip flow regime. For isoflux walls, some closed form expressions for the local and bulk temperature profiles and the Nusselt number in terms of dimensionless slip length, Hartmann number and Brinkman number are given, while the viscous dissipation is also taken into account. Then the analytical solutions derived in this analysis are elaborated. It turns out that since the contribution of the viscous dissipation on the Nusselt number under the given circumstances, especially a stronger electromagnetic field, may reach to nearly 10%, therefore, the viscous heating should be taken into consideration. Otherwise, the heat transfer rate may be overestimated or underestimated depending on whether the fluid is being heated or cooled. Also, there are singularities in Nusselt number values, which move close together by including the viscous dissipation. Further, an increase in the Hartmann number increases the convection, which is especially reflected in smaller values of dimensionless slip length.
Keywords: Microchannel; Liquid Slip Flow; Electromagnetic Field; Nusselt Number; Viscous Dissipation
Nonlinear numerical simulation on the onset of Soret-driven motion in a silica nanoparticles suspension by Min Chan Kim (831-835).
The onset of buoyancy-driven convection in an initially quiescent, horizontal silica nanoparticle suspension layer heated from above is analyzed theoretically. In this thermally-stably stratified fluid layer the Soret diffusion can induce buoyancy-driven motion for the case of the negative separation ratio. For the high Rayleigh number the convective motion sets in during the transient diffusion stage and the onset time of this motion is analyzed by employing the nonlinear numerical simulation. It is interesting that the convective motion is very weak and the diffusional process is dominant even after the onset time of convection, τ c , and the nonlinear effects are manifested from the time τ m (>τ c ). The present τ m explains the existing experimental results quite well.
Keywords: Soret-driven Convection; Silica Nanoparticles Suspension; Nonlinear Analysis; Numerical Simulation
TiO2 nanotube-supported V2O5 catalysts for selective NO reduction by NH3 by Liyuan Xiong; Qin Zhong; Qianqiao Chen; Shule Zhang (836-841).
TiO2 nanotubes (TNT) were prepared by hydrothermal method at 140 °C for 23 h. The V2O5/TNT (VTNT) catalysts were obtained by impregnation in NH4VO3 solution. The VTNTs exhibited much higher denitration efficiency than those supported on the raw TiO2, and satisfactory resistance to water and sulfur. Results from BET, TEM, XRD, NH3-TPD and EPR verified that V2O5 was dispersed well on TNT, thus favoring NH3 adsorption, promoting the transformation from V5+ to V4+, conducing to the formation of oxygen vacancies and superoxide radicals in the presence of NH3 and O2, and then resulting in the high catalytic activity of VTNTs.
Keywords: TNT; V2O5 ; Hydrothermal; Dispersion; SCR
Regeneration of catalyst clay soils (Tonsil CO 610 G) by supercritical carbon dioxide by Hamid Rajaei; Ali Akbar Golchehreh; Ali Zeinolabedini Hezave; Feridun Esmaeilzadeh (842-851).
Extraction of deactivatived materials from contaminated clay soils (Tonsil CO 610 G) by supercritical carbon dioxide was investigated. Effect of different conditions including extraction temperature (308.15–338.15 K) and pressure (100–330 bar) (thermodynamic conditions), flow rate (4.2–42.6 cc/min), and static time (45–85 min) were investigated to find the optimum conditions for extraction of deactivatived materials. Based on the different experiments, optimum conditions for flow rate (4.2 cc/min), static time (85 min) and extraction pressure and temperature (330 bar and 313.15 K) were obtained. In addition, the GC-MS analysis and Bromine index (BI) analysis were revealing that the clay soil is activated and could be used as catalyst again.
Keywords: Supercritical Carbon Dioxide; Tonsil CO 610 G; Extraction; Soil Contamination; Regeneration
Continuous phenol hydroxylation over ultrafine TS-1 in a side-stream ceramic membrane reactor by Xiulong Jiang; Fei She; Hong Jiang; Rizhi Chen; Weihong Xing; Wanqin Jin (852-859).
A side-stream ceramic membrane reactor system was developed that can facilitate the in situ separation of ultrafine catalysts from the reaction mixture and make the production process continuous. Continuous hydroxylation of phenol to dihydroxybenzene over ultrafine titanium silicalites-1 (TS-1) was taken as a model reaction to evaluate the feasibility and performance of the membrane reactor system. The effects of membrane pore size and operation conditions (residence time, temperature, catalyst concentration, phenol/H2O2 molar ratio) on the performance of the reactor system were examined via single factor experiments. We demonstrated that the membrane pore size and operation conditions greatly affect the conversion, selectivity and filtration resistance. The phenol conversion and dihydroxybenzene selectivity remain stable at about 11% and 95% in a 20-h continuous run, respectively.
Keywords: TS-1; Phenol Hydroxylation; Membrane Reactor; Ceramic Membrane; Stability
Effect of CeO2 on CO removal over CeO2-modified Ni catalyst in CO-rich syngas by Sung Ho Kim; Weon-Doo Lee; Ho-In Lee (860-863).
A CeO2-modified Ni catalyst has been studied as a substitute for Ni bulk catalyst in a CO removal reaction using various characterization methods. CO removal was enhanced slightly and presented at lower reaction temperatures following promotion of CeO2 on Ni. The enhanced ability to reduce CO was mainly a result of methanation rather than WGS during a CO removal reaction. Based on X-ray diffraction and temperature-programmed reduction, CeO2 appeared to change the Ni surface properties. Because the bond strength between C and O atoms in CO was weakened by the surface oxygen of CeO2 on Ni, the CeO2-promoted Ni catalyst showed higher CO conversion and lower selectivity to WGS than Ni bulk catalyst.
Keywords: Fuel Processor; Water Gas Shift; CO Methanation; Cerium Oxide; Mobile Surface Oxygen
Effect of support for alcohol-hydrocarbon synthesis from syngas in Cu-based catalyst by Sun-Hwa Yeon; Dae-Hyun Shin; Nam-Sun Nho; Kyoung-Hee Shin; Chang-Soo Jin; Sung-Chan Nam (864-870).
Effects of a Cu-based catalyst on the catalytic performance in alcohol-hydrocarbon synthesis from syngas have been investigated, using various supports. Under the different porosities of three supports (zinc oxide, activation carbon, and titanium dioxide), whereas Cu/ZnO produces one liquid phase of major mixed alcohols, Cu/AC and Cu/TiO2 create two phases, alcohol (∼75%) and hydrocarbon (∼25%). X-ray diffraction shows that CuO impregnated on supports undergoes a complete reduction of metallic copper Cu0, which is the real active phase in the catalytic process. The Cu/TiO2 catalyst showed the highest ethanol composition in a mixed alcohol phase under GHSV 18,000 h−1, 30 bar, and 300 °C.
Keywords: Ethanol; Catalyst; Copper; Zinc Oxide; Activated Carbon; Titanium Dioxide; Support
H2S oxidation by multi-wall carbon nanotubes decorated with tungsten sulfide by Ali Mohamadalizadeh; Jafar Towfighi; Morteza Adinehnia; Hamid Reza Bozorgzadeh (871-877).
Tungsten sulfide catalysts decorated on single and multiwall carbon nanotubes (SWNTs & MWNTs) and activated carbon were synthesized, and XRD, ICP, SEM, TEM and ASAP analyses were employed to acquire the characteristics of each catalyst. Afterwards a gas flow containing 5,000 ppm of H2S was passed over the catalyst in gas hour space velocity (GHSV) of 5,000 h−1, temperature of 65 °C, steam volume percent of 20 and O2/H2S ratio equal to 2. The results revealed that the catalyst supported on MWNTs exhibited higher conversion amongst its counterparts. Then effects of GHSV, steam volume percent in the feed, catalyst loading and temperature were investigated on conversion of hydrogen sulfide to elemental sulfur for tungsten sulfide catalyst decorated on MWNTs.
Keywords: Hydrogen Sulfide; Oxidation; Carbon Nanotubes
Thermal degradation characteristic of Tetra Pak panel boards under inert atmosphere by Aysel Kantürk Figen; Evren Terzi; Nural Yilgör; Saip Nami Kartal; Sabriye Pişkin (878-890).
hermal degradation characteristics of Tetra Pak panel boards (TPPB) can be useful to improve usage of such panels as an alternative to wood-based products such as plywood, fiberboard, and particleboard. In the study, samples from the TPBBs manufactured from waste Tetra Pak packages (WTPP) were heated in a nitrogen atmosphere at different heating rates (10, 15 and 20 °C/min) using a thermal analysis system. The Coats-Redfern kinetic model was applied to calculate kinetic parameters. The degradation rate equations were then established. In addition, the kinetic compensation effect (KCE) was used to correlate the pre-exponential factor (k o ) with activation energy (E a ) and the existence of the KCE was accepted. TG-FT/IR analyses were applied to the TPPB degradation and then the FT-IR stack plot was used to analyze gas products (CO2, CH4, HCOOH, and CH3OH). Infrared vibrational frequencies and the micro, crystal structure of the TPPBs were investigated by Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM) and X-Ray diffraction analysis (XRD), respectively.
Keywords: Tetra Pak; Panel Board; Thermal Degradation; Coats-Redfern; FT-IR
Evaluation of physical properties and adsorption capacity of regenerated granular activated carbons (GACs) by Seon-Ha Chae; Seong-Su Kim; Woochang Jeong; No-Suk Park (891-897).
The objectives of this study were to evaluate the variation in physical properties and investigate the adsorption capacity after regeneration of granular activated carbon (GAC). A correlation analysis was conducted to examine the relationship between the iodide number and loss rate. The experimental results showed that the loss rate of regenerated carbon should be related to the usage time of GAC. Physical properties including the effective size and uniformity coefficient were similar to those of virgin GAC. This result indicates that the function of GAC as an adsorption medium may be recovered completely. Although the iodine number and specific surface area of the regenerated GAC were smaller than those of virgin GAC, the cumulative pore volume of the former was larger. The removal efficiency of organic matter from the regenerated GAC column was equal to or slightly higher than that from the virgin GAC column. Consequently, regeneration may increase the number of mesopores which are responsible for the removal of organic matter.
Keywords: Granular Activated Carbon (GAC); Regeneration; Physical Properties; Adsorption Capacity; Iodide Number
The removal of perchlorate using amine-functionalized mesoporous anion-exchange resins with different number of ligands by Byunghwan Lee; Sang Don Lee; Kwang-Ho Choo (898-905).
Perchlorate anion (ClO 4 t- ) in water has become an environmental issue because it can impair proper functioning of the thyroid gland. For the removal of perchlorate anions from water, adsorption using anion-exchange resins has been generally used as the most suitable method. We have prepared mesoporous anion-exchange resins via simple functionalization of amine ligands with different numbers of functional groups, and used them for the removal of perchlorate anions from aqueous solutions. The physical and chemical properties of the prepared samples were measured using nitrogen adsorption-desorption measurement, elemental analyses, X-ray diffraction, and Fourier transform infrared spectroscopy. We also investigated equilibrium isotherms for the measurement of adsorption capacities and kinetic performances of the prepared samples. The prepared materials showed fast adsorption kinetic performances, and M-3N among the prepared materials exhibited high perchlorate adsorption capacity of 175.4mg/g compared with the results of the previous reports.
Keywords: Perchlorate; Mesoporous Materials; Amine Ligands; Anion-exchange Resin
Effects of fruiting body extracts of Lentinus edodes cultivated using corn cob on biological activities by Jong-Soo Kim; Dubok Choi; Bock-Gie Jung; Bong-Joo Lee; Geum-Sook Lim; Myung Koo Lee; Wol-Suk Cha; Hoon Cho (906-912).
We investigated the antioxidant, nitrite scavenging, immune-enhancing and antimicrobial effects of the Lentinus edodes fruiting body extracts (LEFB extract) cultivated in the solid state using corn cob. The CAT, SOD and GSH-Px activities in the LEFB extract (400mg)-fed group were approximately 1.70, 1.64, and 2.2 times higher than those of the control group. The nitrite scavenging activity was highest (86.4%) when the LEFB extract concentration was 600 μg/mL. The immune-enhancing and antimicrobial effects of LEFB extract after an experimental Bordetella bronchiseptica infection were examined. White blood and neutrophil in the LEFB extract (400 mg)-fed group were approximately 2.1 and 2.2 times higher, respectively, than those of the control group. The total leukocyte was 30% higher than that of the control group. The CD4: CD8 ratio in the LEFB extract (200 mg)-fed group was increased approximately 54.3% compared to that of the control group. The levels of TNF-α and IFN-γ mRNA expression in the LEFB extract (400 mg)-fed group were approximately 49 and 50% lower than those of the control group. The bacteria and inflammatory cell in the LEFB extract (400 mg)-fed group were approximately 48.7 and 29% lower, respectively, than that of the control group. These results suggest that the LEFB extract may be useful in immune function improvement.
Keywords: Lentinus edodes ; Corn Cob; Antioxidant Activity; Nitrite Scavenging Activity; Immune-enhancing Activity; Antimicrobial Effect
Production of cyclic adenosine-3′,5′-monophosphate by whole cell catalysis using recombinant Escherichia coli overexpressing adenylate cyclase by Nan Li; Ying He; Yong Chen; Xiaochun Chen; Jianxin Bai; Jinglan Wu; Jingjing Xie; Hanjie Ying (913-917).
Adenylate cyclase (EC 126.96.36.199) catalyzes the formation of cyclic adenosine-3′,5′-monophosphate (cAMP) from adenosine 5′-triphosphate (ATP). Recombinant Escherichia coli overexpressing adenylate cyclase was used to synthesize cAMP by whole cell catalysis. Some key parameters were examined during the catalytic process, while pH and Mg2+ were found to influence cAMP production significantly. Optimum conditions were pH 8.52 and 30 °C with 77.2 mM Mg2+ in 100 mM Tris-HCl buffer, including 0.25% Triton-X 100 as detergent and 30 mM pyruvate sodium as enzyme activator for 6 h. 14.93 g/L of cAMP was produced with a conversion rate of 91.5%. The current work provided a potential way for the industrial production of cAMP.
Keywords: cAMP; Adenylate Cyclase; Whole Cell Catalysis; Bioconversion
Chiral adsorption of phenylalanine by α-, β-cyclodextrin modified layered double hydroxides by Xiaolei Liu; Lili Meng (918-924).
The chiral adsorption of racemic phenylalanine (Phe) by carboxymethyl-α/β-cyclodextrin-intercalated Zn-Al layered double hydroxides (CM-α/β-CD-LDHs) has been studied. The adsorption isotherms of chiral excess adsorption and the total adsorption of Phe by these CM-α/β-CD-LDHs have been investigated. CM—CD-LDHs were found to be more suitable for chiral recognition of Phe than CM—CD-LDHs. Furthermore, the intraparticle diffusion model is successfully validated in this work. Intraparticle effective diffusivities (D eff ) of Phe in these CM-α/β-CD-LDHs macroparticles were determined from the homogeneous Fickian diffusion model at various temperatures.
Keywords: LDHs; Adsorption; Parallel Diffusion; Phenylalanine; Chiral
Hydrotropic effect and thermodynamic analysis on the solubility and mass transfer coefficient enhancement of ethylbenzene by Antony Bertie Morais; Chinnakannu Jayakumar; Nagarajan Nagendra Gandhi (925-930).
Concentrated aqueous solutions of a large number of hydrotropic agents, urea, nicotinamide, and sodium salicylate, have been employed to enhance the aqueous solubilities of poorly water soluble organic compounds. The influence of a wide range of hydrotrope concentrations (0–3.0mol·L−1) and different system temperatures (303–333 K) on the solubility of ethylbenzene has been studied. The solubility of ethylbenzene increases with increase in hydrotrope concentration and also with system temperature. Consequent to the increase in the solubility of ethylbenzene, the mass transfer coefficient was also found to increase with increase in hydrotrope concentration at 303 K. The enhancement factor, which is the ratio of the value in the presence and absence of a hydrotrope, is reported for both solubility and mass transfer coefficient of ethylbenzene. The Setschenow constant, K s , a measure of the effectiveness of a hydrotrope, was determined for each case. To ascertain the hydrotropic aggregation behavior of ethylbenzene, thermodynamic parameters such as Gibb’s free energy, enthalpy, and entropy of ethylbenzene were determined.
Keywords: Ethylbenzene; Hydrotropy; Solubility; Mass Transfer Coefficient; Sodium Salicylate
Measurement and correlation of solubility of xylitol in binary water+ethanol solvent mixtures between 278.00 K and 323.00K by Zhanzhong Wang; Qian Wang; Xiangshan Liu; Wenzhi Fang; Yan Li; Huazhi Xiao (931-936).
The solubility of xylitol in ethanol+water solvent mixtures was measured at temperatures ranging from 278.00 K to 323.00 K at atmospheric pressure by using a laser technique. The results of these measurements were correlated by the combined nearly ideal binary solvent CNIBS/Redlich-Kister equation. The experimental solubility and correlation equation in this work can be used as essential data and models in the purification process of xylitol. The variant 2 in the CNIBS/R-K models was confirmed to be more adaptable to predict solubility of xylitol in binary ethanol +water system. Using the experimentally measured solubilities, the thermodynamic properties of dissolution of xylitol, such as Gibbs energy, molar enthalpy of dissolution, and molar entropy of dissolution, were calculated.
Keywords: Xylitol; Solubility; Measurement; Correlation; Thermodynamic Properties
Hydrogen recovery from Tehran refinery off-gas using pressure swing adsorption, gas absorption and membrane separation technologies: Simulation and economic evaluation by Ali Mivechian; Majid Pakizeh (937-948).
Hydrogen recovery from Tehran refinery off-gas was studied using simulation of PSA (pressure swing adsorption), gas absorption processes and modeling as well as simulation of polymeric membrane process. Simulation of PSA process resulted in a product with purity of 0.994 and recovery of 0.789. In this process, mole fraction profiles of all components along the adsorption bed were investigated. Furthermore, the effect of adsorption pressure on hydrogen recovery and purity was examined. By simulation of one-stage membrane process using co-current model, a hydrogen purity of 0.983 and recovery of 0.95 were obtained for stage cut of 0.7. Also, flow rates and mole fractions were investigated both in permeate and retentate. Then, effects of pressure ratio and membrane area on product purity and recovery were studied. In the simulation of the gas absorption process, gasoline was used as a solvent and product with hydrogen purity of 0.95 and recovery of 0.942 was obtained. Also, the effects of solvent flow rate, absorption temperature, and pressure on product purity and recovery were studied. Finally, these three processes were compared economically. The results showed that the PSA process with total cost of US$ 1.29 per 1 kg recovered H2 is more economical than the other two processes (feed flow rate of 115.99 kmol/h with H2 purity of 72.4 mol%).
Keywords: Hydrogen Separation; PSA; Membrane; Gas Absorption; Off-gas
Synthesis and characterization of CdSe nanocrystals in the presence of butylamine as a capping agent by Nguyen Tam Nguyen Truong; Woo Kyoung Kim; Chinho Park (949-954).
TOPO-capped cadmium selenide (CdSe) nanocrystals of sizes between 3 and 8 nm have been synthesized, and the surface-capping molecule, trioctylphosphine oxide, was replaced by butylamine. The effects of changing the surface ligands of the synthesized CdSe nanocrystals on the structural, optical, and electrical properties were investigated. The shift toward shorter wavelength (higher energy) in the visible range of the optical absorption band edge was observed by UV-Vis spectroscopy, and a blue-shift of the photoluminescence peaks was observed with luminescent quenching. Surface modification was found to cause an increase in the surface energy of nanocrystals, resulting in the improvement in charge carrier separation and cell performance in applications towards bulk hetero-junction solar cells.
Keywords: Ligand Exchange; Nanocrystal; Blue-shift; Band Edge; Photoluminescence Quenching
Determination of kinetic parameters during the thermal decomposition of epoxy/carbon fiber composite material by Jae Hun Lee; Kwang Seok Kim; Hyo Kim (955-962).
An in-depth study to determine the thermal decomposition kinetics parameters such as the activation energy E a , the reaction order n, and the pre-exponential factor A of epoxy/carbon fiber composite material has been conducted. We employ not only the modified peak property method that is proposed here, but also the conventional method in analyzing the experimental data, and compare the results to show the performance of the proposed model. The pyrolysis tests for the epoxy/carbon fiber composite materials are conducted by using thermogravimetric analyser at various heating rates. As a result, the best prediction to the experimental data can be obtained by the modified peak property method. Besides, among the methods applied here, the modified peak property method provides most convenient way to recover the parameters: it does not require a curve fitting of the data nor a long iterative computation.
Keywords: Kinetic Parameters; Modified Peak Property Method; Epoxy/Carbon Fiber; TGA
Comparisons of particle cluster diameter and concentration in circulating fluidized bed riser and downer using computational fluid dynamics simulation by Benjapon Chalermsinsuwan; Dimitri Gidaspow; Pornpote Piumsomboon (963-975).
The information of particle cluster dynamics is necessary for improving the performance of a circulating fluidized bed system. The main objective of this study is to compare the particle cluster diameters and concentrations from computational fluid dynamics simulation results between circulating fluidized bed riser and downer. The calculation methodologies are based on the concept of kinetic theory of granular flow and statistics. The mathematical model was verified by using the experimental dataset from literature and used for computing the particle cluster dynamics. In the circulating fluidized bed riser and downer, a dense and dilute core-annulus flow structures were obtained, respectively. The particle cluster in the circulating fluidized bed riser possessed more heterogeneity movements than that in the circulating fluidized bed downer. This can be explained by the system flow direction. About the particle cluster dynamics, the particle cluster diameters and concentrations in the circulating fluidized bed riser were higher than the ones in the downer. The calculated values were comparable to the empirical correlations. This confirms the validity of the calculation methodologies. Particle cluster dynamics and its example application inside circulating fluidized bed riser and downer were also discussed.
Keywords: Circulating Fluidized Bed; Computational Fluid Dynamics; Downer j]Particle Cluster; Riser; Simulation