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Showing papers in "Korean Journal of Chemical Engineering in 2009"


Journal ArticleDOI
TL;DR: In this article, the authors obtained colloidal silver nanoparticles by chemical reduction of silver nitrate in water with sodium borohydride (NaBH4) in the presence of sodium dodecyl sulfate (SDS) as a stabilizer.
Abstract: Colloidal silver nanoparticles were obtained by chemical reduction of silver nitrate in water with sodium borohydride (NaBH4) in the presence of sodium dodecyl sulfate (SDS) as a stabilizer. The obtained nanoparticles were characterized by their UV-vis absorption spectra and transmission electron micrograph (TEM) images. The UV-vis absorption spectra showed that NaBH4 served not only as a reducing agent but also as a stabilizer, which protects the aggregation of silver nanoparticles. The TEM images showed that the particles were dispersed better with increasing the NaBH4 concentration.

277 citations


Journal ArticleDOI
TL;DR: In this paper, a fractionation according to solubility and polarity has been used to separate bitumen into its fractions, and the polarity fractionation using Fuller's earth allows bitumen to separate into SARA components (saturates, aromatics, resins, asphaltenes).
Abstract: Separation and chemical analysis was investigated using bitumen samples from Athabasca oil sand in Alberta. Fractionation according to solubility and polarity has been used to separate bitumen into its fractions. The solvent de-asphaltening was performed by n-pentane solvent (solubility fractionation), and the polarity fractionation using Fuller’s earth allows maltene to separate into SARA components (saturates, aromatics, resins and asphaltenes). The SARA components are analyzed comprehensively using elemental analysis (EA), Fourier-transformed infrared (FTIR), ultraviolet-visible spectroscopy (UV-vis), high performance chromatography (HPLC) and thermogravimetric analysis (TGA). EA (C, H, N, S), heavy metals (Ni, V) concentrations, FT-IR and UV-vis tests provided the explanation of chemical composition. From IR spectra, maltene and saturates/aromatics (sat/aro) contained more aliphatic compounds than resin or asphaltene. Also, IR spectrum of sat/aro was similar to crude oil and VGO (vacuum gas oil). Different UV signal data clearly indicates the contribution of aromatic constituents in the fractions. Using optimized analysis conditions of HPLC, we successfully separated the peaks for bitumen and its fractions. The characteristic peak pattern of SARA (saturates, aromatics, resins, asphaltenes) fractions was observed, and also the peak pattern of sat/aro was similar to that of crude oil and VGO. However, TGA results revealed that thermal behavior for sat/aro was similar to that of crude oil but different from that of VGO. Also, from the comparison between decomposition temperature of TGA and boiling point, their correspondence was found.

95 citations


Journal ArticleDOI
TL;DR: The addition of agar, a viscous polysaccharide, into SFW medium is effective for the production of BC, and this scale-up method is very useful for the mass production in a 50 L spherical type bubble column bioreactor by decreasing the shear stress and increasing the kLa.
Abstract: Bacterial cellulose (BC) was produced by Acetobacter xylinum KJ1 in a modified airlift-type bubble column bioreactor, which had a low shear stress and high oxygen transfer rate (k L a). Saccharified food wastes (SFW) were used as the BC production medium due to its low cost. An aeration rate of 1.2 vvm (6 L/min) was tentatively determined as the optimal aeration condition in a 10 L spherical type bubble column bioreactor, by analysis of the oxygen transfer coefficient. When 0.4% agar was added, the BC production reached 5.8 g/L, compared with 5.0 g/L in the culture without the addition of agar. The BC productivity was improved by 10% in the addition of 0.4% agar into the SFW medium. Then, by conversion of a linear velocity of 0.93 cm/sec, from the relationship between the linear velocity and oxygen transfer rate, 1.0 vvm (30 L/min) was determined as an optimal aeration condition in a 50 L spherical type bubble column reactor. Using SFW medium, with the addition of 0.4% agar, and air supplied of 1.0 vvm, 5.6 g/L BC was produced in the 50 L spherical type bubble column bioreactor after 3 days of cultivation, which was similar to that produced in the 10 L bioreactor. In conclusion, the addition of agar, a viscous polysaccharide, into SFW medium is effective for the production of BC, and this scale-up method is very useful for the mass production in a 50 L spherical type bubble column bioreactor by decreasing the shear stress and increasing the k L a.

66 citations


Journal ArticleDOI
TL;DR: In this paper, an electrocoagulation process for the removal of iron from drinking water with aluminum alloy as the anode and stainless steel as the cathode was provided, and the results showed that the maximum removal efficiency of 98.8% was achieved at a current density of 0.06 A dm−2, at a pH of 6.5.
Abstract: The present study provides an electrocoagulation process for the removal of iron from drinking water with aluminum alloy as the anode and stainless steel as the cathode. The studies were carried out as a function of pH, temperature and current density. The adsorption capacity was evaluated with both the Langmuir and the Freundlich isotherm models. The results showed that the maximum removal efficiency of 98.8% was achieved at a current density of 0.06 A dm−2, at a pH of 6.5. The adsorption of iron preferably fitting the Langmuir adsorption isotherm suggests monolayer coverage of adsorbed molecules. The adsorption process follows second-order kinetics. Temperature studies showed that adsorption was endothermic and spontaneous in nature.

64 citations


Journal ArticleDOI
TL;DR: In this article, an Eulerian multiphase approach based on kinetic theory of granular flow was used to simulate flow of coal-water slurries (CWS) in horizontal pipelines.
Abstract: An Eulerian multiphase approach based on kinetic theory of granular flow was used to simulate flow of coal-water slurries (CWS) in horizontal pipelines. The RNG k-ɛ turbulent model was incorporated in the governing equation to model turbulent two-phase flow with strong particle-particle interactions. In this model, the coal particles with bimodal distribution were considered as two solid-phase components, and the moment exchange between solid and liquid as well as that between solid and solid were accounted for. The model was firstly validated with pressure gradient and concentration profile data from the open literature, and then validated with pressure gradient data of the authors’ experiments. The effects of influx velocity, total influx concentration and grain composition were numerically investigated, and the results have displayed some important slurry flow characteristics, such as constituent particle concentration distribution and velocity distribution as well as pressure gradients, which are very difficult to display in the experiments. The results suggest that both gravity difference between large and small particles and strong particle-particle interaction had significant effects on concentration distribution as well as velocity distribution.

63 citations


Journal ArticleDOI
TL;DR: An empirical model has been developed for the successful prediction of the melt index during grade change operations in a high density polyethylene plant and two different schemes have been proposed which are compared with other techniques to exhibit their superiority.
Abstract: An empirical model has been developed for the successful prediction of the melt index (MI) during grade change operations in a high density polyethylene plant. To efficiently capture the nonlinearity and grade-changing characteristics of the polymerization process, the plant operation data is treated with the recursive partial least square (RPLS) scheme combined with model output bias updating. In this work two different schemes have been proposed. The first scheme makes use of an arbitrary threshold value which selects one of the two updating methods according to the process requirement so as to minimize the root mean square error (RMSE). In the second scheme, the number of RPLS updating runs is minimized to make the soft sensor time efficient, while reducing, maintaining or normally increasing the RMSE obtained from first scheme up to some extent. These schemes are compared with other techniques to exhibit their superiority.

61 citations


Journal ArticleDOI
TL;DR: In this paper, an approach to evaluate the jet stability of the drop-on-demand (DOD) inkjet printing has been proposed, based on which the transient behavior of the DOD drop formation has been studied experimentally for Newtonian liquids with a range of different viscosities but of a comparable surface tension.
Abstract: Inkjet printing has been widely used in many applications and has been studied for many years. However, there are not many systematic researches on the mechanism of jet formation, nor is there any reliable platform that enables us to evaluate jet performance. In this study, an approach to practically evaluate the jet stability of the dropon-demand (DOD) inkjet printing has been proposed, based on which the transient behavior of the DOD drop formation has been studied experimentally for Newtonian liquids with a range of different viscosities (1.0–11 cp) but of a comparable surface tension. For more viscous liquids, the rate of the jet retraction after a pinch-off from the nozzle was found to increase as the thread motion became more sharp and conical as a result of the shape effect. The break-up time of the jet also increased because the rate of capillary wave propagation was lower for more viscous liquids. The jet stability graph, which can be drawn in terms of jet retraction and break-up time, was employed to characterize the jetting stability, and the degree of satellite drop generation was quantitatively evaluated by two critical jet speeds. The effect of an electric pulse imposed on a piezoelectric plate inside the printhead was also studied. The single-peak electric pulse was used in this experiment for simple analysis, and the jet speed variation was measured under different operating conditions. Both the optimal dwell time and the maximum stable jetting frequency were affected by viscosity and they were explained in terms of the propagation theory.

54 citations


Journal ArticleDOI
TL;DR: The development of a fermentation strategy for hyaluronic acid (HA) production by Streptococcus zooepidemicus ATCC 39920 has been explored and it was found that the timing of medium exchange is critical for successfully performing fill-and-draw operations.
Abstract: The development of a fermentation strategy for hyaluronic acid (HA) production by Streptococcus zooepidemicus ATCC 39920 has been explored. The specific HA productivity (Y P/X ) was affected by the medium carbon-tonitrogen (C/N) ratio rather than the specific growth rate of cells. Accordingly, HA fermentation should be performed in a balanced medium with an optimum C/N ratio of 2: 1 in a batch culture. To improve the performance of the batch culture, the operation conditions for the fill-and-draw culture were investigated. It was found that the timing of medium exchange is critical for successfully performing fill-and-draw operations. Since streptococcal cells at the stationary phase might lose the capacity of HA synthesis, the displacement of the medium in a fill-and-draw culture should be started at the late exponential growth phase.

47 citations


Journal ArticleDOI
TL;DR: In this article, the applicability of the multi-wavelength Near-infrared sensor to analyze coal properties such as proximate analysis (moisture, ash, volatile matter, fixed carbon), ultimate analysis (carbon, hydrogen, nitrogen, oxygen, sulfur) and heating value is discussed.
Abstract: The applicability of the Multi-wavelength Near-infrared sensor to analyze coal properties such as proximate analysis (moisture, ash, volatile matter, fixed carbon), ultimate analysis (carbon, hydrogen, nitrogen, oxygen, sulfur) and heating value is discussed. The most useful wavelengths (1,680, 1,942, 2,100, 2,180, 2,300 nm) for determining coal properties concentration were chosen by analyzing the NIR spectrum according to coal properties. Absorbances at the characteristic wavelength obtained from 128 mixed coal samples, which are using at a conventional thermal power plant, were correlated to the coal properties by using multiple regression analysis. The accuracy of coal analysis was examined by calculating the RMSEC (%), RMSEP (%), comparing the error with ASTM/ISO tolerance and performing paired Student’s T-test. The result of on-line coal analysis for all moisture, volatile matter, fixed carbon, carbon, hydrogen and heating value is not different from that of ASTM/ISO traditional methods at 90% confidence level. The technology appears suitable for the determination of several coal prorperties. If calibrated periodically, this on-line analysis of coal properties is helpful to efficiently operate a coal fired power plant.

45 citations


Journal ArticleDOI
TL;DR: In this article, two commercial nanofiltration membranes (NF90 and NF270) have been investigated in detail to study their performance in filtering aqueous solutions containing different salt mixtures in a cross-flow NF membrane process within the pressure range from 4 to 9 bar.
Abstract: Nanofiltration (NF) membranes have recently been employed as pretreatment unit operations in seawater desalination processes and as partial demineralization to seawater. The present paper investigates the performance of selected commercial NF membranes to reject salts of high concentrations at salinity levels representative of brackish and sea water. Two commercial nanofiltration membranes (NF90 and NF270) have been investigated in detail to study their performance in filtering aqueous solutions containing different salt mixtures in a cross-flow NF membrane process within the pressure range from 4 to 9 bar. Spiegler-Kedem model (SKM) was used to fit the experimental data of rejection with the permeate flux. The results showed that NF90 membrane was shown to have a distinct ability to reject both monovalent and divalent ions of all investigated mixtures with very reasonable values but with relatively low flux. This will make NF90 more suitable for the application in the pretreatment of desalination processes. On the other hand, NF270 can reject monovalent ions at relatively low values and divalent ions at reasonable values, but at very high permeate flux. The SKM model only fitted well the experimental data of divalent ions in salt mixture. Based on the evaluation of the overall performance of NF90 and NF270 membranes, their distinct ability to reject salts at high salinity from seawater is considered an advantage in the field of pretreatment of seawater feed to desalination units.

45 citations


Journal ArticleDOI
Qilei Song1, Rui Xiao1, Zhongyi Deng1, Laihong Shen1, Mingyao Zhang1 
TL;DR: In this paper, an experimental study of CaSO4 oxygen carrier in CLC of methane was conducted in a laboratory scale fixed bed reactor, where the oxygen carrier particles were exposed in six cycles of alternating reduction methane and oxidation air.
Abstract: Chemical-looping combustion (CLC) is a promising technology for the combustion of gas or solid fuel with efficient use of energy and inherent separation of CO2. A reactivity study of CaSO4 oxygen carrier in CLC of methane was conducted in a laboratory scale fixed bed reactor. The oxygen carrier particles were exposed in six cycles of alternating reduction methane and oxidation air. A majority of CH4 reacted with CaSO4 to form CO2 and H2O. The oxidation was incomplete, possibly due to the CaSO4 product layer. The reactivity of CaSO4 oxygen carrier increased for the initial cycles but slightly decreased after four cycles. The product gas yields of CO2, CH4, and CO with cycles were analyzed. Carbon deposition during the reduction period was confirmed with the combustible gas (CO+H2) in the product gas and slight CO2 formed during the early stage of oxidation. The mechanism of carbon deposition and effect was also discussed. SO2 release behavior during reduction and oxidation was investigated, and the possible formation mechanism and mitigation method was discussed. The oxygen carrier conversion after the reduction decreased gradually in the cyclic test while it could not restore its oxygen capacity after the oxidation. The mass-based reaction rates during the reduction and oxidation also demonstrated the variation of reactivity of CaSO4 oxygen carrier. XRD analysis illustrated the phase change of CaSO4 oxygen carrier. CaS was the main reduction product, while a slight amount of CaO also formed in the cyclic test. ESEM analysis demonstrated the surface change of particles during the cyclic test. The reacted particles tested in the fixed bed reactor were not uniform in porosity. EDS analysis demonstrated the transfer of oxygen from CaSO4 to fuel gas while leaving CaS as the dominant reduced product. The results show that CaSO4 oxygen carrier may be an interesting candidate for oxygen carrier in CLC.

Journal ArticleDOI
TL;DR: In this paper, the effects of types of promoters such as platinum, cobalt, and iron on biomass gasification were evaluated, and the impregnation and coprecipitation methods showed superior performance.
Abstract: Metallic nickel has been selected as a catalyst for biomass gasification because of its activity in biomass steam gasification and tar reduction. The effects of types of promoters such as platinum, cobalt, and iron on biomass gasification were evaluated. The area of interest was the effects of preparation methods, which were impregnation and coprecipitation. Catalyst preparation by the impregnation method showed superior performance. The conclusion can be drawn from the experiments that the platinum promoter enhanced the reforming reaction, iron promoted a water-gas shift reaction, and the cobalt promoter favored a methanation reaction. Moreover, the addition of noble metal reduced carbon deposition on Ni/dolomite.

Journal ArticleDOI
TL;DR: In this article, the effect of bed height on CO2 capture was investigated by carbonation/regeneration cyclic operations using a bubbling fluidized bed reactor, which was manufactured by the Korea Electric Power Research Institute.
Abstract: The effect of bed height on CO2 capture was investigated by carbonation/regeneration cyclic operations using a bubbling fluidized bed reactor. We used a potassium-based solid sorbent, SorbKX35T5 which was manufactured by the Korea Electric Power Research Institute. The sorbent consists of 35% K2CO3 for absorption and 65% supporters for mechanical strength. We used a fluidized bed reactor with an inner diameter of 0.05 m and a height of 0.8 m which was made of quartz and placed inside of a furnace. The operating temperatures were fixed at 70 °C and 150 °C for carbonation and regeneration, respectively. The carbonation/regeneration cyclic operations were performed three times at four different L/D (length vs diameter) ratios such as one, two, three, and four. The amount of CO2 captured was the most when L/D ratio was one, while the period of maintaining 100% CO2 removal was the longest as 6 minutes when L/D ratio was three. At each cycle, CO2 sorption capacity (g CO2/g sorbent) was decreased as L/D ratio was increased. The results obtained in this study can be applied to design and operate a large scale CO2 capture process composed of two fluidized bed reactors.

Journal ArticleDOI
TL;DR: Investigation of fed-batch cultivation for the increased productivity of bacterial cellulose (BC) sheets by Gluconacetobacter hansenii PJK in static conditions using chemically defined medium and waste from beer fermentation broth found that waste fromBeer fermentation broth is a superior medium for the BC production using fed- batch cultivation.
Abstract: The current study investigated fed-batch cultivation for the increased productivity of bacterial cellulose (BC) sheets by Gluconacetobacter hansenii PJK in static conditions using chemically defined medium and waste from beer fermentation broth. Fermentations were carried out in a 3 L jar fermenter without any impeller for 30 days. In the proposed fed-batch cultivation, 500 mL of the medium was initially inoculated with pre-culture in a jar fermenter while a fresh medium was fed periodically. BC production was also done by using batch cultivation which was used as a control for comparison. The results obtained revealed an overall of 2–3 times increase in BC production in fed-batch cultivation compared to batch cultivation after 30 days of cultivation. During these experiments, it was found that waste from beer fermentation broth is a superior medium for the BC production using fed-batch cultivation. The production of water soluble oligosaccharides as useful by-products was also monitored during these investigations. Fed-batch cultivation and waste from beer fermentation was also found superior for the production of these by-products. According to literature search and to the best of our knowledge, it is the first report of using fed-batch cultivation for BC production in static conditions.

Journal ArticleDOI
TL;DR: In this paper, the kinetics of the thermal decomposition of Alberta oil sand has been investigated by thermogravimetric analysis (TGA) for the study of oil sand pyrolysis characteristics.
Abstract: The kinetics of the thermal decomposition of Alberta oil sand has been investigated by thermogravimetric analysis (TGA) for the study of oil sand pyrolysis characteristics. The TGA experiments were carried out at four different heating rates of 10, 20, 30, 40 °C/min up to 900 °C to verify weight variation and reaction temperature. The activation energy of the thermal decomposition of Alberta oil sand obtained from the kinetic analysis was similar to that of the previous researches. Also, bitumen was extracted by solvent (toluene, THF (tetrahydrofuran)) and analyzed. Extracted bitumen was analyzed by using proximate analysis, ultimate analysis, heavy metal analysis, heating value, asphaltenes, API, SIMDIS, density, TLC, and molecular weight. The analyses of the extracted bitumen were similar to those of heavy residue.

Journal ArticleDOI
TL;DR: In this article, the solubility of carbon dioxide in three ionic liquids (ILs) under supercritical fluid condition was measured at pressures up to 32 MPa and at temperatures of 313.15, 323.15 and 333.15 K in a high-pressure view cell.
Abstract: The solubility of carbon dioxide in three ionic liquids (ILs) under supercritical fluid condition was meas- ured at pressures up to 32 MPa and at temperatures of 313.15, 323.15, and 333.15 K in a high-pressure view cell. The imidazolium-derivative ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate ((bmim)(PF6)), 1-butyl-3-meth- ylimidazolium tetrafluoroborate ((bmim)(BF4)), and 1-octyl-3-methylimidazolium tetrafluoroborate ((omim)(BF4)) were employed in this research. The effects of pressure, temperature, nature of anion and cation as well as the water content on the solubility of CO2 in the ILs were investigated experimentally. The solubility of CO2 in the IL was higher for the ILs with longer cationic alkyl group and for the ILs with lower anion polarity. The lower the water content or the lower the temperature as well as the higher the pressure, the higher was the solubility of CO2.

Journal ArticleDOI
TL;DR: In this article, a two-level factorial design experiment was used to preliminarily screen the influence and interaction among the factors, such as initial temperature, feed concentration, and feed rate.
Abstract: Pressure swing adsorption (PSA) is attractive for final separation in the process of water removal especially for fuel ethanol production. Despite many researches on simulation and experimental works on adsorption of water on 3A zeolite in a fixed bed, none have studied a process with the actual PSA system. The purpose of this research was to study the PSA process with two adsorbers and effects of several parameters. The research also included analysis of kinetic and thermodynamic data of ethanol-water adsorption on commercial 3A zeolites in a single fixed bed. A two-level factorial design experiment was used in this research work to preliminarily screen the influence and interaction among the factors. Effects of important parameters such as initial temperature, feed concentration and feed rate were investigated. It was proven that the Langmuir isotherm could best predict the experimental results. In the PSA pilot test, the principal factors, which had effects on the performance, were feed rate, feed concentration, adsorption pressure and the cycle time. Prediction of the process efficiency in terms of ethanol recovery and enrichment was proposed in the form of regression models. The results of the study in a fixed bed adsorber could help designing a pilot-scale PSA unit. The experiments proved to be successful in terms of producing high concentration ethanol with high percentage of ethanol recovery. With further simulation work the process could be scaled up for an industrial use.

Journal ArticleDOI
TL;DR: In this paper, the hydrodynamics of a bubbling gas-solid fluidized bed of 57.4 μm FCC particles were simulated by using a two-fluid model integrating the kinetic theory of granular flow for particulate phase stresses.
Abstract: The hydrodynamics of a bubbling gas-solid fluidized bed of 57.4 μm FCC particles was simulated by using a state-of-the-art two-fluid model integrating the kinetic theory of granular flow for particulate phase stresses. The overestimation of the bed expansion was resolved by using a suitable scale factor in the drag model as suggested by McKeen and Pugsley (T.R. McKeen, T.S. Pugsley, Powder Technol., 129, 139 (2003)). This study showed that the method was appropriate in simulation of a gas-solid fluidized bed of Geldart A particles at high gas velocities (0.3 to 0.61 m/s). The reduction of computational time especially for simulation of large-scale systems was achieved. The time-averaged local voidage was compared with the experimental data and the trend of varying several parameters on the hydrodynamic of the bed was investigated. The simulation results showed both qualitative and quantitative agreement with the literature.

Journal ArticleDOI
TL;DR: In this article, the effect of hydrogen peroxide dosage applied and the reaction pH together with the iron oxidation state on the degradation level was analyzed for synthetic solutions of phenol, o-, m- and p-cresol.
Abstract: Synthetic solutions of phenol, o-, m- and p-cresol were oxidised by using Fenton’s reagent. The application of substoichiometric dosage of H2O2 led to the formation of intermediate compounds, continuing later the oxidation to complete oxidation. An important objective was to analyze the effect of hydrogen peroxide dosage applied and the reaction pH together with the iron oxidation state on the degradation level. A kinetic model was derived from a reaction mechanism postulated which was used to analyze the results of the experiments. Another aim was to analyze the hydrogen peroxide consumption. Noteworthy results include an increase in oxidant consumption to intensify phenol removal. Furthermore, oxidant consumption was analyzed through the ratio H2O2 to phenol removed and the average specific rate of removal (ASRR). By analyzing these two parameters it has been possible to ascertain the most favorable strategy for an efficient application of H2O2.

Journal ArticleDOI
TL;DR: The incorporation of oxygen functional groups onto the surface of eucalyptus activated carbon and its sur- face chemistry were investigated as a function of oxidation conditions, carbon porous properties and carbon preparation method as mentioned in this paper.
Abstract: The incorporation of oxygen functional groups onto the surface of eucalyptus activated carbon and its sur- face chemistry were investigated as a function of oxidation conditions, carbon porous properties and carbon preparation method. Under all treatment conditions of increasing time, temperature and oxidant concentration, liquid oxidation with HNO3, H2O2 and (NH4)2S2O8 and air oxidation led to the increase of acidic group concentration, with carboxylic acid showing the largest percentage increase and air oxidation at the maximum allowable temperature of 350 o C pro- duced the maximum content of both carboxylic acid and total acidic group. Nitric acid oxidation of chemically activated carbon produced higher total acidic content but a lower amount of carboxylic acid compared to the oxidized carbon from physical activation. The increased contents of acidic groups on oxidized carbons greatly enhanced the adsorption capacity of water vapor and heavy metal ions.

Journal ArticleDOI
TL;DR: In this article, the authors developed a simulation model through a kinetics model of the ASPEN plus simulator, performed to detect operating characteristics of DME direct synthesis, which is referenced by experimental data of 3 ton/day (TPD) coal gasification pilot plant located at IAE in Korea.
Abstract: DME (Dimethyl Ether) has emerged as a clean alternative fuel for diesel. There are largely two methods for DME synthesis. A direct method of DME synthesis has been recently developed that has a more compact process than the indirect method. However, the direct method of DME synthesis has not yet been optimized at the face of its performance: yield and production rate of DME. In this study it is developed a simulation model through a kinetics model of the ASPEN plus simulator, performed to detect operating characteristics of DME direct synthesis. An overall DME synthesis process is referenced by experimental data of 3 ton/day (TPD) coal gasification pilot plant located at IAE in Korea. Supplying condition of DME synthesis model is equivalently set to 80 N/m3 of syngas which is derived from a coal gasification plant. In the simulation it is assumed that the overall DME synthesis process proceeds with steadystate, vapor-solid reaction with DME catalyst. The physical properties of reactants are governed by Soave-Redlich-Kwong (SRK) EOS in this model. A reaction model of DME synthesis is considered that is applied with the LHHW (Langmuir-Hinshelwood Hougen Watson) equation as an adsorption-desorption model on the surface of the DME catalyst. After adjusting the kinetics of the DME synthesis reaction among reactants with experimental data, the kinetics of the governing reactions inner DME reactor are modified and coupled with the entire DME synthesis reaction. For validating simulation results of the DME synthesis model, the obtained simulation results are compared with experimental results: conversion ratio, DME yield and DME production rate. Then, a sensitivity analysis is performed by effects of operating variables such as pressure, temperature of the reactor, void fraction of catalyst and H2/CO ratio of supplied syngas with modified model. According to simulation results, optimum operating conditions of DME reactor are obtained in the range of 265–275 °C and 60 kg/cm2. And DME production rate has a maximum value in the range of 1–1.5 of H2/CO ratio in the syngas composition.

Journal ArticleDOI
TL;DR: In this article, an equation of state applicable to the system containing electrolytes has been developed by coupling the perturbed chain statistical associating fluid theory (PC-SAFT) with the primitive mean spherical approximation.
Abstract: In this work an equation of state applicable to the system containing electrolytes has been developed by coupling the perturbed chain statistical associating fluid theory (PC-SAFT) with the primitive mean spherical approximation. The resulting electrolyte equation of state is characterized by 4 ion parameters for each of the cation and anion contained in aqueous solutions, and 4 ion specific parameters for each of six cations (Li+, Na+, K+, Rb+, Mg2+ and Ca2+) and six anions (Cl−, Br−, I−, HCO 3 − , NO 3 − and SO 4 2− ) were estimated, based upon the individual ion approach, from the fitting of experimental densities and mean ionic activity coefficients of 26 aqueous single-salt solutions at 298.15 K and 1 bar. The present equation of state with the estimated individual ion parameters has been found to satisfactorily describe not only the densities and mean ionic activity coefficients, but also osmotic coefficients and water activities of single-salt aqueous solutions. Furthermore, the present model was extended to two-salt aqueous solutions, and it has been found that thermodynamic properties such as mentioned above, of two-salt solutions, can be well predicted with the present model, without any additional adjustable parameters.

Journal ArticleDOI
Qian Liu1, Shurong Wang1, Kaige Wang1, Zhongyang Luo1, Kefa Cen1 
TL;DR: Based on the Van Soest method, the components in Chinese fir and fast-growing poplar were quantified, and the fiber present was separated into three fractions: neutral detergent fiber, acid detergent fibre and strong acid detergents fiber as mentioned in this paper.
Abstract: Based on the Van Soest method, the components in Chinese fir and fast-growing poplar were quantified, and the fiber present was separated into three fractions: neutral detergent fiber, acid detergent fiber and strong acid detergent fiber. Microstructure of the fibers was investigated by a Fourier transform infrared spectrometry. Cellulose and hemicellulose both represent the characteristics of polysaccharides, while lignin has dissimilar structure. Pyrolysis of fir, poplar and the detergent fibers was carried out on a thermogravimetric analyzer coupled with FTIR spectrometry. After the removal of extractives and soluble minerals, pyrolysis of NDF shows the characteristics of the three main components. Hydrocarbons, aldehydes, ketones, acids, alcohols and others are generated due to the primary pyrolysis of hemicellulose and cellulose in single stages. Phenols and alcohols are the dominant volatiles released from pyrolysis of lignin in two successive stages, respectively.

Journal ArticleDOI
TL;DR: In this article, a phenol-formaldehyde resin (PFR) and bituminous coal (SH) were pyrolyzed at various temperatures and the micro-structure of the resulting char was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectrograms.
Abstract: A phenol-formaldehyde resin (PFR) and a bituminous coal (SH) were pyrolyzed at various temperatures. The structure and the char-NO reactivity were analyzed in order to examine the effect of pyrolysis temperature on the micro-structure of the resulting char and further on the reactivity towards NO. Micro-structure of the char samples was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Raman spectroscopy. It was indicated that the micro-structure of PFR char and coal char experienced remarkable changes during pyrolysis, which resulted in the decrease of phenolic OH, aromatic hydrogen and more ordered structure. The pyrolysis temperature showed a weak impact on the reactivity of PFR char but comparatively remarkable impact on that of coal char at lower reaction temperature. Mineral matter in coal char presented a weak effect on the reactivity.

Journal ArticleDOI
TL;DR: In this article, both monolayers and multilayers were obtained from a dilute solution of n-octadecyltrichlorosilane [OTS, CH3(CH2)17SiCl3] on a SiO2/Si surface after a low pressure O2 plasma treatment.
Abstract: Both monolayers and multilayers were obtained from a dilute solution of n-octadecyltrichlorosilane [OTS, CH3(CH2)17SiCl3] on a SiO2/Si surface after a low pressure O2 plasma treatment. A close-packed monolayer of good quality was formed on the SiO2/Si surface. The resulting self-assembled layers were characterized by goniometry, atomic force microscopy (AFM), ellipsometry and Fourier transformed infrared attenuated total reflection (FTIR-ATR) spectroscopy. An examination of the time-dependent water contact angle measurements as a function of the OTS concentration revealed rapid monolayer formation at the initial stage. The contact angle measurements showed that the surface structure of the OTS monolayer was quite resistant to environmental changes as a result of the polymerization of OTS molecules and the formation of covalent bonds between the monolayer and substrate surface. The surface was covered with islands (observed by AFM) that were in-filled to produce in a smooth surface. The FRIR-ATR spectra showed symmetric (νs(CH2)) and asymmetric (νas(CH2)) components perpendicular to the surface.

Journal ArticleDOI
TL;DR: In this paper, the optimal batch mode temperature was between 30 and 32 o C with a maximum power density of 418-470 mW/m 2, obtained at an external resistor of 1,000 Ω, as the Pt loading on the cathode electrode was increased from 0.5 to 3.0 mg.
Abstract: The microbial fuel cell (MFC) has attracted research attention as a biotechnology capable of converting hydrocarbon into electricity production by using metal reducing bacteria as a biocatalyst. Electricity generation using a microbial fuel cell (MFC) was investigated with acetate as the fuel and Geobacter sulfurreducens as the biocatalyst on the anode electrode. Stable current production of 0.20-0.24 mA was obtained at 30-32 o C. The maximum power density of 418-470 mW/m 2 , obtained at an external resistor of 1,000 Ω, was increased over 2-fold (from 418 to 866 mW/m 2 ) as the Pt loading on the cathode electrode was increased from 0.5 to 3.0 mg Pt/cm 2 . The optimal batch mode temperature was between 30 and 32 o C with a maximum power density of 418-470 mW/m 2 . The optimal tempera- ture and Pt loading for MFC were determined in this study. Our results demonstrate that the cathode reaction related through the Pt loading on the cathode electrode is a bottleneck for the MFC's performance.

Journal ArticleDOI
TL;DR: In conclusion, BC production by the modified bubble column culture mode of 50 L brought more favorable results in terms of the physical properties and its ease of scale-up.
Abstract: The saccharogenic liquid obtained by the enzymatic saccharification of food wastes was used as a medium for production of bacterial cellulose (BC). The enzymatic saccharification of food wastes (SFW) was carried out by the cultivation supernatant of Trichoderma inhamatum KSJ1. 5.6 g/L of BC was produced in a new modified 50 L bubble column bioreactor by Acetobacter xylinum KJ1. The productivity was similar to that of a modified 10 L bubble column bioreactor (5.8 g/L). When pure oxygen was supplied into the scaled-up culture conditions, 6.8 g/L (12% enhancement) of BC was produced, indicating a very useful method for BC mass production. The oxygen uptake rate (OUR) and qO2 (specific oxygen uptake rate) were 0.214 mg-DO/L·min and 0.257 mg-DO/g-cell·min, respectively. The physical properties, such as morphology, molecular weight, crystallinity, and tensile strength of BCs produced in static culture (A), 10 L (B) and 50 L (C) modified bubble column cultures were investigated. All BCs showed fibrils with highly networking structure. The number average molecular weight of BCs in A, B and C was 2,314,000, 1,878,000, and 1,765,000, respectively. All of the BCs had a form of cellulose I representing pure cellulose. The relative degree of crystallinity showed the range of 79.6–86.0%. Tensile strengths of BC sheet in A, B and C were 1.75, 1.21, and 1.19 kg/mm2, respectively. In conclusion, BC production by the modified bubble column culture mode of 50 L brought more favorable results in terms of the physical properties and its ease of scale-up.

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TL;DR: In this article, the effect of pH, dye concentration, sorbent dosage, temperature and contact time on the dye removal efficiency has been studied and it was found that adsorbent derived from guava leaves is more efficient in removal of dye.
Abstract: Removal of auramine dye from aqueous waste solutions was investigated by using very cheap and bio- sorbent, withered guava tree leaves and activated carbon. Guava leaves are readily available in the western and northern parts of India throughout the year, and hence form a cost effective alternative for removal of dyes from waste waters. The optimum contact time was found to be 120 min. in a pH range of 8-9 for 92-94% removal of the dye from aqueous solutions containing 150 mg/L of auramine dye using 2 g of the adsorbent. The effect of pH, dye concentration, sorbent dosage, temperature and contact time on the dye removal efficiency has been studied. Experimental results were found to fit both Freundlich and Langmuir models. Since the dye contains a cationic species, the removal efficiency was highest in a pH range of 8-9. Continuous adsorption studies in a packed column showed 100% removal efficiency for a flow rate of 10 ml·min −1 . When compared with the activated carbon, it was also found that adsorbent derived from guava leaves is more efficient in removal of dye.

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TL;DR: In this article, an accelerated single cell test and single electrode cell test were carried out to investigate membrane degradation by Pt dissolved/deposited on the membrane, which revealed that Pt particles were deposited in the membrane at the anode side, with a decrease in F, O, and C content near the anodes side of the membrane.
Abstract: An accelerated single cell test and single electrode cell test were carried out to investigate membrane degradation by Pt dissolved/deposited on the membrane. For a cell operating under accelerated conditions (OCV, 90°C, anode RH 0%, cathode O2 supply), MEA analyses revealed that Pt particles were deposited in the membrane at the anode side, with a decrease in F, O, and C content near the anode side of the membrane. Dissolved Pt from the cathode showed that Pt existed mainly in the form of Pt2+ ionic species. Oxygen and hydrogen helped Pt dissolution from the cathode and Pt deposition in the membrane, respectively. Radical formation on deposited Pt in the membrane was detected by electron spin resonance (ESR). Fluoride emission rate (FER, an indicator of membrane degradation rate) increased with an increase in the amount of Pt in the membrane.

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TL;DR: In this paper, the microparticle formation of HMX using supercritical antisolvent (SAS) recrystallization process was performed and the effect of organic solvent on the size and morphology of prepared particles was observed.
Abstract: Supercritical fluid processes have gained great attention as a new and environmentally benign method of preparing the microparticles of energetic materials like explosives and propellants. In this work, HMX (cyclotetramethylenetetranitramine) was selected as a target explosive. The microparticle formation of HMX using supercritical antisolvent (SAS) recrystallization process was performed and the effect of organic solvent on the size and morphology of prepared particles was observed. The organic solvents used in this work were dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), cyclohexanone, acetone, and N-methyl pyrrolidone (NMP).