bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of NaCl precipitation on vapour–liquid dechlorination of CHClF2
Authors: Nishiumi Hideo , Kato Ryo 
Published: February 2003

AbstractA dechlorination process for chlorinated compounds such as the chlorinated fluorocarbons (CFCs) is proposed. In this process, CFCs are dissolved in alcohols and irradiation with UV promotes their decomposition at room temperature and atmospheric pressure. Remarkably, irradiation is unnecessary to decompose chlorodifluoromethane, CHClF2 (HCFC22 or R22), which gives NaCl and 1,1‐difluorodimethyl ether CH3OCHF2 as products. In this work, experiments were carried out on the vapour–liquid reaction to produce the fluoroether CH3OCHF2 from HCFC22. The reaction was found to have no side reactions. The initial decomposition rate obtained from experimental results indicated that the reaction rate was proportional to the concentration of both NaOH and dissolved HCFC22. However, as the reaction proceeded, the reaction rate decreased more than expected from the initial reaction rate. Assuming that the produced NaCl precipitation created poor mixing of the methanol solutions, the volumetric coefficient KLa was measured and a model developed based on mass transfer relations. Calculated results showed that the model qualitatively agreed with the reaction rate data.© 2003 Society of Chemical Industry
Dramatic innovation of propene epoxidation efficiency derived from a forced flow membrane reactor
Authors: Kobayashi Masayoshi , Togawa Junya , Kanno Tohru , Horiuchi Jun‐ichi , Tada Kiyosi 
Published: February 2003

AbstractIt is possible to develop a selective epoxidation process for propene using heterogeneous catalysis in a forced‐flow membrane reactor. The most innovative processes required two catalysts, Cs–Ag and Re–Ag, which were immobilized in the membrane pores of a micro‐porous glassy (MPG) substance, and three different reactor systems for reaction gas flows in the membrane pores. The systems included a convection‐flow reactor (CFR), a diffusion‐flow reactor (DFR), and a packed‐bed‐flow reactor (PFR). The three types were examined over temperatures ranges from 420 to 525 K, while keeping the total conversion of propene to less than 10%. The membrane reactor systems followed two common Langmuir‐type equations of reaction rates for CO2 and propylene oxide (PO) formation under steady state operations at atmospheric pressure. The amount of the intermediate for CO2 formation, whose structure retained the CCC bond of a propene molecule, was sensitively controlled by the types of catalysts and reactor systems used. Comparing the three immobilized catalysts, Cs–Ag, Re–Ag, and Ag2O, the larger the amount of intermediate formed on the catalysts the higher was the propylene oxide (PO) selectivity and thus the PO selectivity followed the order of Re–Ag > Cs–Ag > Ag2O. The CFR with Re–Ag/MPG clearly demonstrated hysteresis kinetics depending on the increase (C‐up) or decrease (C‐down) in the propene concentration. The PO selectivity was separately evaluated as 73–35% for the C‐up and 35–21% for the C‐down. The convection flow rate of reactants in the pores effectively contributed to an enhancement of the PO production rate from 18 to 41% of PO selectivity, for the reactant flow rate of 70–130 cm3 min−1 at 483 K.© 2003 Society of Chemical Industry
Multi‐objective optimization of venturi scrubbers using a three‐dimensional model for collection efficiency
Authors: Ravi Gopalan , Viswanathan Shekar , Gupta Santosh K , Ray Madhumita B 
Published: February 2003

AbstractMulti‐objective optimization of a venturi scrubber was carried out using a three‐dimensional model for collection efficiency and non‐dominated sorting genetic algorithm (NSGA). Two objective functions, namely (a) maximization of the overall collection efficiency, and (b) minimization of the pressure drop were used in this study. Three decision variables including two operating parameters, viz liquid–gas ratio and gas velocity in the throat, and the nozzle configuration, which takes into account the three‐dimensional nature of the problem, were used in the optimization. Optimal design curves (non‐dominated Pareto sets) and the values of the decision variables corresponding to optimum conditions on the Pareto set for a pilot‐scale scrubber were obtained. The liquid to gas (L/G) ratio, which is a key decision variable that determines the uniformity of liquid distribution, and a staggered nozzle configuration can produce uniform liquid distribution in the scrubber. Multiple penetration using nozzles of two different sizes in a triangular staggered arrangement can reduce liquid loading by as much as 50%, consequently reducing the pressure drop in the scrubber.© 2003 Society of Chemical Industry
Performance enhancement of a chemical reactor utilizing flow instability
Authors: Kabir Mohammad F , Ray Ajay K 
Published: February 2003

AbstractA detailed analysis has been performed for a heterogeneous photocatalytic Taylor vortex reactor that uses flow instability to recirculate fluid continually from the vicinity of the rotating inner cylindrical surface to the stationary outer cylindrical surface of an annulus. A comprehensive time accurate computation shows the different stages of flow evolution and the effects of finite length of the reactor in creating eddies, the overall effects of which shows very high efficiency of photocatalytic conversion. The physical arrangement considered is such that pollutant degradation is maximized by a combination of the Controlled Periodic Illumination (CPI) effect and the motion of fluid particles in a specific regime of centrifugal instability.© 2003 Society of Chemical Industry
On modelling turbulent flow in an oscillatory baffled column – RANS model or large‐eddy simulation?
Authors: Jian Hongbing , Ni Xiong‐Wei 
Published: February 2003

AbstractOscillatory flow in a baffled column can achieve intensive and uniform mixing with lower shear rate in comparison to the traditional stirred tank reactors (STR). The flow in an oscillatory baffled column (OBC) is unsteady with periodicity in both time and space. Mixing is achieved by the formation of eddies. It is therefore very important to understand the turbulence in an OBC as it determines the degree of segregation, breakage of droplets and bubbles, and the efficiency of chemical/biochemical reactions. Modelling of turbulence is usually associated with the traditional Reynolds Averaged Navier–Stokes (RANS) model. Our results show that the RANS turbulence models, which are sufficiently good for simulating flows in STR, are very poor in predicting periodic flows in an OBC as the methodology of averaging in time in RANS has effectively removed the turbulence. In OBC, eddies of various sizes are the main ingredient for mixing, the large‐eddy simulation (LES) is particularly suitable for such type of flows. In this paper, we describe our understanding on the way in which the LES works.© 2003 Society of Chemical Industry
Using non‐intrusive laser‐induced fluorescence in the characterisation of mixing in an oscillatory baffled column
Authors: Fitch A W , Ni X 
Published: February 2003

AbstractTraditionally the characterisation of mixing in a system is achieved by injecting a tracer solution and monitoring the changes of tracer concentration with time using conductivity probes. In this paper we demonstrate that a non‐intrusive laser‐induced fluorescence (LIF) technique can be used to quantify the behaviour of viscous fluids in a model oscillatory baffled column (OBC). The OBC is an alternative‐mixing device in which longitudinal periodic fluid oscillations are transposed onto a column with evenly spaced ‘doughnut’ shaped baffles. This combination of baffles and oscillation generates an enhanced yet uniform mixing system. In LIF, a dye fluoresces when it is induced by a laser. The intensity of the light emitted can be converted into the concentration of the dye. The timed profile of average concentration (within a baffled cell) leads to the determination of the mixing time and axial dispersion coefficient. This paper attempts to show that LIF is a powerful tool in studying mixing.© 2003 Society of Chemical Industry
Improved simulation of a vapour permeation module
Authors: Brinkmann Torsten , Dijkstra Marga , Ebert Katrin , Ohlrogge Klaus 
Published: February 2003

AbstractAn increasing number of hybrid processes consisting of conventional unit operations and vapour permeation modules have been suggested in recent years. To facilitate accurate process design, rigorous models of this novel membrane process are essential. By comparing experimental results obtained from a pilot plant, it was shown that simply solving the material balances and assuming constant permeances is not sufficient to predict the operating behaviour of a vapour permeation module. In order to reflect the experimental results it was necessary to consider the concentration, temperature and pressure dependency of the permeation process through the membrane as well as the mass transfer restriction in the boundary layer on the feed side. The introduced model is capable of taking account of these effects and predicts the experimental results satisfactorily. The model was written using the commercial, equation‐oriented process simulator Aspen Custom Modeler™ and hence can easily be integrated with commercial process simulation packages.© 2003 Society of Chemical Industry
Process intensification of biodiesel production using a continuous oscillatory flow reactor
Authors: Harvey Adam P , Mackley Malcolm R , Seliger Thomas 
Published: February 2003

AbstractOscillatory flow reactors (OFRs) are a novel type of continuous reactor, consisting of tubes containing equally spaced orifice plate baffles. An oscillatory motion is superimposed upon the net flow of the process fluid, creating flow patterns conducive to efficient heat and mass transfer, whilst maintaining plug flow. Unlike conventional plug flow reactors, where a minimum Reynolds number must be maintained, the degree of mixing is independent of the net flow, allowing long residence times to be achieved in a reactor of greatly reduced length‐to‐diameter ratio. Many long residence time processes are currently performed in batch, as conventional designs of plug flow reactor prove to be impractical due to their high length‐to‐diameter ratios, which lead to problems such as high capital cost, large ‘footprint’, high pumping costs and, also control is difficult. The OFR allows these processes to be converted to continuous, thereby intensifying the process. The transesterification of various natural oils to form ‘biodiesel’ is a ‘long’ reaction, usually performed in batch. Conversion to continuous processing should improve the economics of the process, as the improved mixing should generate a better product (rendering the downstream separation processes easier), at lower residence time (reduction in reactor volume). These improvements can decrease the price of ‘biodiesel’, making it a more realistic competitor to ‘petrodiesel’. This paper shows that it is feasible to perform this reaction in an OFR at a lower residence time. The reaction was performed in a pilot‐scale plant, using rapeseed oil and methanol as the feedstocks, and NaOH as the catalyst.© 2003 Society of Chemical Industry
Modelling a novel miniaturised reactor/separator system
Authors: Schuster Andreas , Lakshmanan Ramachandran , Ponton Jack , Sefiane Khellil 
Published: February 2003

AbstractThe use of microreactors for industrially relevant chemical production processes has been investigated. Recent research has shown that miniaturised reactors support process intensification and successful applications involve the synthesis of unit operations. Following a study of candidate processes for miniaturisation, this investigation focussed on the direct fluorination that consists of a complex set of reactions. A novel catalytic membrane microreactor configuration has been developed to address the contacting of the gas/liquid/solid phases. The membrane separates the gas phase from the liquid phase, presenting a well‐defined interface to the catalyst. A simplified model has been developed to study the advantages of the catalytic membrane for an isothermal parallel reaction system, where an electrophilic reaction leads to the desired product but competes with a fast radical reaction mechanism. If no catalyst is used the selectivity can be improved by limiting the fluorine concentration. The separation of the reactants results in higher selectivities at higher conversion compared with a mixed feed process (ie bubble column).© 2003 Society of Chemical Industry
The use of pine bark as a natural adsorbent for persistent organic pollutants – study of lindane and heptachlor adsorption
Authors: Ratola Nuno , Botelho Cidália , Alves Arminda 
Published: February 2003

AbstractPine bark obtained as a sawmill by‐product in the north of Portugal was used for the adsorption of lindane and heptachlor, two organochlorine pesticides classified as POPs (Persistent Organic Pollutants), from aqueous solutions. It is intended that this natural adsorbent be used as an alternative to activated carbon in an innovative approach for the removal of these classes of compounds, reducing significantly the regeneration costs of the process, thus providing for its intensification. The analytical methodology validated for pesticides' quantification consisted of solid‐phase microextraction (SPME) prior to gas chromatography with electron capture detection (GC‐ECD), which presented limits of detection for lindane and heptachlor of 0.067 µg dm−3 and 0.062 µg dm−3, respectively. Repeatability, reproducibility and recovery were the parameters tested for validation, yielding better results for lindane. For the bark particle size used (125–300 µm), the average efficiency of removal attained for lindane was 80.6%, and 93.6% for heptachlor with the equilibrium time set at 24 h. Both Langmuir and Freundlich models were tested for the adsorption isotherm, but only the second approach produced reliable results for the adsorption parameters. Values obtained for log Kow were 3.17 for lindane (R2 = 0.9927) and 4.85 for heptachlor (R2 = 0.9401).© 2003 Society of Chemical Industry
Experimental study on drag reduction in a duct
Authors: Mai Jianqiang , Früh Wolf‐Gerrit 
Published: February 2003

AbstractThe present study investigates drag forces on liquids pumped through a duct coated with a magnetic liquid of kinematic viscosity of 1.69 cSt. Due to a suitable arrangement of a set of permanent magnets, the magnetic liquid formed a fluid layer on the bottom of a square duct through which a silicone oil with a kinematic viscosity of 50 cst was pumped. Applied magnetic flux densities ranged from less than 0.01 T to about 0.15 T at the surface of the magnets. The influences of the strength and gradient of the magnetic field, and of the fluid flow rate, on the shape of the magnetic fluid have been investigated. It was found that it is not practical to form a uniform magnetic fluid layer under our experimental conditions, and consequently the drag was increased compared with the uncoated case because the flow of the silicone fluid over the magnetic fluid layer deformed this layer dramatically. For a viscosity ratio between the main flow and the ferrofluid less than about 30, it is therefore not feasible to use a magnetic fluid layer to reduce the drag in a duct. However, the generally high thermal conductivity of magnetic liquids, its convection, and interface deformation, might be exploited for heat transfer enhancement.© 2003 Society of Chemical Industry
Competitive complexation/solvation theory of solvent extraction: general statements, acid extraction by amines, influence of active solvents and temperature
Authors: Kislik Vladimir , Eyal Aharon 
Published: February 2003

AbstractA novel competitive complexation/solvation theory has been developed for interpretation, simulation and preliminary quantification of extraction systems. This theory is based on the modified competitive preferential solvation theory, the concept of amphoteric properties of extractants and the concept of the formation of different aggregation structures on increasing extractant loading. The theory establishes correlation between complexation and solvation. Co‐solvent independence allows direct comparison of the complexing/solvating power (competition order) of various solvents, used as extractants, enhancers (synergistic agents), and diluents. Once determined and tabulated, solute/solvent affinity constant ratio data may be used in any system containing these components. Mathematical descriptions of classical and the presented theories are compared and discussed. Some acid–amine extraction systems are analyzed based on the theory statements presented. The model provides a key for preliminary quantitative prediction of suitable extraction systems. Data, available from the literature and from experiments, were used.© 2003 Society of Chemical Industry
Population balance modelling of droplets in an oscillatory baffled reactor—using direct measurements of breakage rate constants
Authors: Mignard Dimitri , Amin Lekhraj , Ni Xiong‐Wei 
Published: February 2003

AbstractPopulation balance modelling (PBM) is a useful tool for design and prediction in a range of processes that involve dispersed phases, particulates or micro‐organisms. In the Inverse Problem approach, constants related to the rates of evolution and/or interaction of the individual components are optimized so as to match the experimentally observed distribution curves. However, the significance of these results may be slight, or several solutions may be possible. In this paper, a method is presented to circumvent this problem, and is applied to the breakage and coalescence of oil droplets in a continuous oscillatory baffled reactor (OBR). Direct observation of droplet breakage using a high‐speed camera should enable breakage rate constants to be obtained independently from the Inverse Problem approach, and thus obtain more reliable coalescence rate constants. An analysis of the droplet size distributions (DSDs) is also combined with direct observation with the high‐speed camera to allow the development of a breakage model specific to the OBR. It is expected that this method should yield parameters useful for prediction of steady‐state DSDs, and hence enhance the accuracy of design, scale‐up, and prediction of operation.© 2003 Society of Chemical Industry
Particle‐scale modelling of gas–solid flow in fluidisation
Authors: Yu A B , Xu B H 
Published: February 2003

AbstractVarious approaches have been proposed to model the gas–solid two‐phase flow at different time and length scales, including the so‐called two‐fluid model (TFM), direct numerical simulation (DNS) and combined continuum and discrete model (CCDM). This paper briefly discusses the key features of these models and their relative merit with special reference to modelling gas fluidisation. Focus is then given to CCDM in which the motion of individual particles is obtained by solving Newton's second law of motion and fluid flow by the Navier–Stokes equation based on the concept of local average. The applicability of CCDM is highlighted by its successful simulation of complicated phenomena associated with the transition between fluid‐like and solid‐like behaviour in raceway formation and bed expansion. At the same time, the usefulness of the resulting particle‐scale information is demonstrated in elucidating the fundamentals governing the gas–solid flow. Finally, areas for future development are discussed.© 2003 Society of Chemical Industry
Distribution of hepatitis B virus (HBV) genotypes among HBV carriers in the cote d'Ivoire: Complete genome sequence and phylogenetic relatedness of HBV genotype E
Authors: Suzuki Seiji , Sugauchi Fuminaka , Orito Etsuro , Kato Hideaki , Usuda Sadakazu , Siransy Liliane , Arita Isao , Sakamoto Yuko , Yoshihara Namiko , El‐Gohary Ahmed , Ueda Ryuzo , Mizokami Masashi 
Published: February 2003

AbstractThe characteristics of hepatitis B virus (HBV) genotype E are not well known because only a few studies have been carried out by complete genome analysis. The aim of this study was to elucidate the distribution of HBV genotypes in Cote d'Ivoire, and to clarify the genotype‐related characteristics of genotype E. The distribution of HBV genotypes among 48 HBV carriers in Cote d'Ivoire was determined using serological and genetic methods. The characteristics of genotype E were evaluated by complete genome sequences, and further investigations of small S gene, basic core promoter (BCP) mutation, and precore mutation were undertaken. HBV genotype distribution among the 48 carriers was 6.3% for genotype A, 6.3% for genotype D, and 87.4% for genotype E. Complete genomes of two genotype E strains were sequenced, and found to have 98.2% to 99.2% homology at the nucleotide level when compared with genotype E strains reported previously. In 24 genotype E carriers, the precore mutation was detected in 75% of the patients without HBeAg, in contrast to only 25% of the patients with HBeAg (P < 0.05). All 24 strains have T at nucleotide 1858 in the precore region. In contrast, BCP double mutation was detected in 17% of the patients with HBeAg, and 33% of the patients without HBeAg. These results indicated as the following: (1) genotypes A, D, and E of HBV exist in Cote d'Ivoire and genotype E is the most prevalent; (2) genotype E spread with low genetic diversity over the complete genome in West Africa; (3) HBV precore and/or BCP double variants were common among the patients with genotype E infections. J. Med. Virol. 69:459–465, 2003. © 2003 Wiley‐Liss, Inc.
Secular trend of age‐specific prevalence of hepatitis B surface and e antigenemia in pregnant women in Taiwan
Authors: Lin Ho‐Hsiung , Kao Jia‐Horng , Chang Ting‐Chen , Hsu Hong‐Yuan , Chen Ding‐Shinn 
Published: February 2003

AbstractTo elucidate the impact of aging of hepatitis B carrier women on their viral replicative markers in a hepatitis B endemic area, all the parturients admitted to the Hospital were studied from 1985 to 2000. Serum hepatitis B surface (HBsAg) and hepatitis B e antigen (HBeAg) were tested by radioimmunoassay. Mann‐Whitney U and Student's t‐tests were used for statistical analysis. The results showed the yearly prevalence rate of HBsAg in pregnant women seemed stable with a mean of 12.0 ± 1.1% during the period. The yearly positive rate of HBeAg among HBsAg‐positive pregnant women varied between 30.4% and 42.6% from 1985 to 1992 and declined from 29.6% in 1993 to 18.1% in 2000. The mean ratio of HBeAg/HBsAg in carrier parturients was 24.7% [intraquantile range (IQR) 20.5–28.4] from 1993 to 2000, which was significantly lower than that of 32.4% (IQR 31.0–39.0) from 1985 to 1992 (P < 0.0001). The mean age of HBeAg‐positive primiparas from 1993 to 2000 was 29.1 ± 3.9 years and significantly higher than that of 28.0 ± 3.7 years from 1985 to 1993 (P < 0.001), as well as in secundiparas 31.2 ± 3.8 years vs. 30.1 ± 3.4 years (P < 0.001) and in total parturients 30.3 ± 4.2 years vs. 29.3 ± 3.8 years (P < 0.001). Thus, no significant decrease of HBsAg carriage was observed in the past 16 years, whereas a decreased ratio of HBeAg/HBsAg was noted in carrier parturients in the past 8 years and the elderly HBeAg‐positive parturients from 1993 to 2000 may be the cause. J. Med. Virol. 69:466–470, 2003. © 2003 Wiley‐Liss, Inc.