bluuebunny/crossref_metadata_2025_split huggingface dataset:
An inverse correlation of the enhancement effect of tetrachloromethane as a feedstream additive in the oxidative coupling of methane on silica‐supported alkaline earth and alkali‐alkaline earth catalysts with the polarizing ability of the alkaline earth cations
Authors: Ahmed Shamsuddin , Moffat John B. 
Published: August 2005

AbstractResults are reported for the oxidative coupling of methane on silica‐supported alkaline earths prepared from either their acetates or chlorides with and without alkali metals as dopants and in the absence or presence of carbon tetrachloride (TCM). The addition of small quantities of TCM to the methane feedstream produces increases in the conversion of methane and the selectivities to C2 hydrocarbons which correlate with the increase in cation size and thus are inversely related to the polarizing abilities of the cations.
The effect of gas injection on the flow of immiscible liquids in horizontal pipes
Authors: Nädler Martin , Mewes Dieter 
Published: August 2005

AbstractThe flow of two immiscible liquids and the influence of an additional inserted gas phase in horizontal pipes is investigated. The experiments are carried out in a transparent horizontal pipe with an inner diameter of 59 mm and a total length of 48 m. Experimental results are presented for the flow regimes of the two phase and three phase flow of oil, water and gas mixtures. The effect of phase inversion on the pressure drop is measured. The experimental results obtained for the three phase flow of oil, water and air indicate that drag reduction is possible by injecting gas in laminar flowing mixtures of oil and water. In the aerated slug flow regime of oil, water and air a water dominated and an oil dominated flow system can be distinguished. The pressure drop of the three phase flow system is of the magnitude as the pressure drop of the two phase flow of gas and the dominating liquid phase.
Performance of a venturi jet scrubber for H2S removal by iron‐complex solution
Authors: Nasr Mohammad Reza Jaffari , Abedinzadegan M. 
Published: August 2005

AbstractVenturi jet scrubbers are widely used in chemical industries as an efficient gas‐liquid contacting equipment. They are simple in design, have no moving parts, operate with circulating liquid and are reliable in service. Moreover, due to high relative velocity of liquid and gas, considerable overall mass transfer can be produced. In spite of their wide application, readily usable design data are not available in literature, particularly for units producing a gas flow by their own pumping action. The purpose of this paper is to introduce the equipment and its application for H2S removal. The effects of various parameters such as gas and liquid flow rates as well as pressure on hydrodynamics and mass transfer performance of the equipment are investigated. Results of experiments have been shown graphically.
Heat transfer in turbulent falling films
Authors: Numrich Reiner 
Published: August 2005

AbstractIn condensers with high condensation rates or in falling film evaporators the falling film at the vertical tube wall shows a turbulent flow pattern. For optimal dimensioning of these apparatuses the knowledge and the description of the heat transfer in this turbulent falling film is necessary. Especially in fluids with a low thermal conductivity in liquid phase (i.e. hydrocarbons) the main heat transfer resistance is in the falling film, also if there are several components in gas phase. For calculating the heat transfer usually dimensionless Nusselt equations were used. These equations mainly base on experimental results which were found with water vapour as test fluid. It is shown that these equations fail for fluids with low thermal conductivity resp. high Prandtl numbers. Based on a Nusselt equation for turbulent tube flow a new equation for turbulent film flow is derived. A comparison between calculated and measured data for Prandtl numbers up to 50 shows good agreement.
On‐Line mass spectrometer analysis of gasification gas
Authors: Karlegärd Åsa , Götz Adolf , Bjerle Ingemar 
Published: August 2005

AbstractThe mass spectrometer is capable of making rapid, repetitive multicomponent analyses with measurement times as short as a second or less. Mass spectrometers used to be too expensive to be used for process analyses, but simpler and cheaper versions have been developed during the last decade. Mass spectrometers are commonly used within the petrochemical industry, but their use for fuel gas streams is not so widespread. This paper describes tests on a quadrupole mass spectrometer in three different gasification projects. Calibration methods and analysis accuracies obtained are accounted for. On the basis of the tests, it can be concluded that the quadrupole mass spectrometer is very suitable for continuous analysis of complex process streams. An important result is that the separation of CO and N2, an analysis problem that is traditionally regarded as difficult, worked very well. The analysis frequency was approximately once per minute, which should be enough for most control loops.
Synthesis of tertiary amyl methyl ether (TAME): Influence of internal and external mass transfer resistance
Authors: Oost Carsten , Hoffmann Ulrich 
Published: August 2005

AbstractAn experimental set‐up is presented for the measurement of reaction rates in the liquid phase synthesis of tertiary amyl methyl ether (TAME) from methanol and a mixture of 2‐methyl‐1‐butene and 2‐methyl‐2‐butene using an acidic ion exchange resin (Lewatit SPC 118) as catalyst. The reaction was performed in a continuous‐flow recycle reactor at a temperature of 333.15 K and a pressure of 1.6 MPa. Determination of the age distribution (Fcurve) of the reactor showed that mixed flow is approached at a recycle ratio of R = 10. Experiments were performed to reveal the limits of operating conditions where the various resistances do not affect the rate. In agreement with estimation of Reynolds numbers, hindrance by external mass transfer can be excluded at a volumetric flow rate of 10 ml/min and a recycle ratio of R = 10. The maximum temperature increase of the whole particle resulting from limitation of external heat transfer was estimated to be about 3 K. Variation of the size of resin particles revealed the existence of a critical methanol concentration, above which reaction rates can be determined without influence of internal mass transport phenomena. The maximum temperature increase in the particle was estimated to be 0.3 K.
An improved system for automated peptide synthesis
Authors: Bicciato Silvio , Bagno Andrea , Dettin Monica , Buso Orfeo , Di Bello Carlo 
Published: August 2005

AbstractThis paper describes an original system for automated solid‐phase peptide synthesis (SPPS) that was developed in our laboratories. The synthesizer is equipped with separate activator and batch reactors, and was designed to operate under either manual or computer control. Two metering pumps, which constitute the core of the entire apparatus, provide for the delivery and transfer of reagents and solvents in the appropriate quantities and in the correct sequence, and permit simultaneous condensation and activation operations that result in considerable time saving. Various applications to the synthesis of biologically important peptides, utilizing the most widely used strategies in SPPS, are presented as examples of this improved technology.
Modelling of agglomeration in industrial crystallization from solution
Authors: David René , Marchal Philippe , Marcant Bruno 
Published: August 2005

AbstractA phenomenological approach to evaluating the agglomeration rate of growing crystals is presented. Crystals larger than the Kolmogoroff microscale collide because of the fluctuating velocity field. Bridges between the crystals form as a result of competition between crystalline growth and the turbulent velocity fluctuations on the opposite sides of the agglomerate.Crystals smaller than the Kolmogoroff microscale collide because of viscous laminar microshear stresses within the same turbulent eddy, are kept close together by Van der Waals forces and are joined together by crystalline bridges that grow between them. The strength of these bridges depends on the supersaturation level during the moments following the collision.These two sets of phenomena lead to two different preferential generation mechanisms for agglomerates. One example involving important agglomeration effects is developed for each case: the crystallization of adipic acid belongs to the first group (large crystals), whereas the precipitation of calcium oxalate monohydrate is typical of the second case (small crystals).
Study of the runaway characteristics of suspension polymerisation of styrene
Authors: Nemeth Sandor , Thyrion Fernand C. 
Published: August 2005

AbstractThe safe operation of a batch polymerisation reactor assumes sufficient knowledge about all the possible reactions. An investigation has been made in order to predict, with the aid of a mathematical model based on a detailed reaction mechanism, the runaway ability of a styrene batch suspension polymerisation reactor. The results of the simulation were compared with the experimental data obtained from a bench‐scale test cell.
Adiabatic gas absorption in packed columns with large thermal effects
Authors: Swaminathan Rama , Sadasivam M. , Balakrishnan A. R. 
Published: August 2005

AbstractThe performance of packed bed adiabatic gas absorbers has been analyzed using the enthalpy and material balance equations incorporating a new parameter, fr, defined as the fraction of the heat of absorption that is accounted for in the gas stream. An experimental programme to evaluate fr was carried out and the data correlated. It was found that fr was dependent on the thermo‐physical properties and the hydrodynamic conditions. It is postulated that the mechanism by which this heat transfer occurs is by turbulence at the interface and by entrainment.
Modelling of a woodchip refiner using artificial neural network
Authors: Qian Yu , Tessier Patrick J. C. 
Published: August 2005

AbstractNeural networks can be an attractive alternative to mathematical modelling of complex and poorly understood processes if input/output data can easily be obtained. Woodchip refining falls into this category. The mechanism of the refining process is still being studied and no thorough models have yet been developed. A feed‐forward neural network is proposed for modelling of woodchip refiners. The outputs predicted by the neural network are compared with industrial refiner data. It is also shown that a modified neural network structure can be used to optimize refiner operation and product quality. The advantages and disadvantages of neural network model application in simulation and optimization of industrial processes are discussed.
Amine plant simulation by mass transfer and kinetic approach
Authors: Fathi J. , Baheri H. R. 
Published: August 2005

AbstractA computer program has been developed for the simulation of gas‐liquid absorption columns. The calculations are based on known assumptions and methods – the two‐film theory. Mass and energy balances together with chemical reactions are carried out for each tray of the column. The results obtained from the simulation procedure are compared with those measured at industrial plants. For the items “rich solution temperature” and “calculated number of trays” the agreement of calculated and measured results are satisfactory. However, for the CO2 and H2S content of the streams only few comparisons could be made due to the fact that no measured values are available.
Experimental determination and simulation of explosion limits of benzene‐inert gas‐air mixtures
Authors: Gündüz Gönül , Stickling Johannes , Rennhack Rolf 
Published: August 2005

AbstractIn this work, the influences of inert diluents, N2 and CO2, on the explosion limits of benzene‐air mixtures were investigated at two different initial temperatures. The model of constant flame temperature was tested for the simulation of the experimental data. It was seen that the model fitted the data of the lower explosion limits, but didn't correlate with the data of the upper explosion limits.
Polydispersity effect in facilitated transport through liquid surfactant membranes
Authors: Datta Siddhartha , Sanyal Shyamal K. 
Published: August 2005

AbstractAn advancing reaction‐front model has been proposed in the present study of facilitated transport through liquid surfactant membranes by taking into consideration a size distribution of emulsion drops. The model takes into account the continuous and outer liquid membrane phase resistances along with diffusion through composite emulsion drops. The effect of various dispersion phenomena on the mass transfer rate of solute has been discussed for two different operating conditions corresponding to different drop size distributions but having the same Sauter mean diameter. Membrane leakage is assumed to be negligible.
Conversion of ethane on modified zsm‐5 zeolites: A study of aromatization as a function of reaction media
Authors: Hagen Anke , Roessner Frank , Reschetilowski Wladimir 
Published: August 2005

AbstractEthane was converted into aromatic hydrocarbons on H‐ZSM‐5 and Zn‐ZSM‐5 at 773 K in a flow reactor system using nitrogen and hydrogen as carrier gases. Residence time was varied by changing catalyst weights to obtain information about primary and secondary reaction steps. On H‐ZSM‐5 ethane conversion proceeds via formation of ethene and subsequent oligomerization. Oligomers undergo fast isomerization, cracking and cyclization leading to a broad spectrum of aromatics. Methane is a secondary product. Dehydrogenation reactions proceed irreversibly. Introduction of zinc species significantly enhances the aromatization activity of H‐ZSM‐5 on the one hand and causes a change of reaction mechanism on the other. Oligomerization of olefinic intermediates can take place at zinc sites. In nitrogen, aromatization of C6 olefins is faster than isomerization and cracking of these oligomers. Dehydrogenation steps proceed reversibly. On using hydrogen as the carrier gas over Zn‐ZSM‐5, the conversion of ethane as well as the formation of aromatics decrease. Furthermore, aromatics richer in hydrogen (especially C8 aromatics) are then formed preferentially.
Comparison of methods for characterization of complex mixtures
Authors: Quiroga Mónica E. , Campanella Enrique A. 
Published: August 2005

AbstractComparative calculations of several methods of characterization for three multicomponent mixtures that include paraffin, naphthene, and aromatic fractions are shown. Each method requires different experimental information about the mixtures but all use the numerical Gauss‐Legendre quadrature. The results show that characterization making direct use of the TPB distillation curve is the most suitable approach for characterizing complex multicomponent mixtures.
Three‐step heterogeneous catalytic reaction mechanism with coverage dependent parameters
Authors: Murzin Dmitry Yu. 
Published: August 2005

AbstractA three‐step catalytic reaction (TSCR) mechanism is considered. It involves the steps of adsorption of two different reactants and the bimolecular reaction between adsorbed species. For this mechanism the rates of elementary reactions were assumed to be dependent on the surface coverages of two adspecies due to the repulsive mutual interactions between adsorbed species. The surface electronic gas model was chosen for the description of surface inhomogeneity. It is demonstrated that for such a TSCR mechanism sustained oscillations cannot exit. The application of the model to evaluation of kinetic data is discussed.
A study of gas hold‐up, liquid velocity, and mixing time in a complex high viscosity, fermentation fluid in an airlift bioreactor
Authors: Wang Yuchun , McNeil Brian 
Published: August 2005

AbstractWhole mean gas hold‐up εg, liquid recirculation velocity U1d and mixing time tm were measured in a 0.12 m3 airlift reactor, with an external recirculation loop (ALR‐EL), which was used for the production of the exopolysaccharide, Scleroglucan, by cultivation of the filamentous fungus, Scleroticum glucanicum. Under identical fermentation conditions, the effects of air flowrate and the viscosity of the culture fluid on εg, U1d, and tm were investigated. In the range studied, empirical correlation for εg, U1d and tm with both superficial velocity Ugr and consistency coefficient K were obtained and expressed separately.
Optimization strategies and their application to heat exchanger network synthesis
Authors: Roosen Peter , Groß Bernd 
Published: August 2005

AbstractHeat exchanger network synthesis (HENS) is a frequently encountered class of chemical engineering optimization targets. Besides its immediate relevance to practical, industrial applications, the HENS problem presents an adequate complexity class to test new technique of numerical optimization and benchmark them.This paper first sketches two established approaches to HEN optimization. The fist one is based on thermodynamic insight, while the second one uses MINLP techniques for rigid optimization. Afterwards an alternative approach based on the paradigm of evolutionary optimization is introduced. The newly developed optimizer module is coupled to the well known ASPEN PLUS simulator. The program package allows the optimization of parameters as well as network structure.
Energy system analysis is fertilizer complex – pinch analysis vs. Exergy analysis
Authors: Radgen Peter , Lucas Klaus 
Published: August 2005

AbstractA critical comparison of the strength and weakness of two optimization strategies for thermochemical process is made, i.e. pinch analysis and exergy analysis. Although both methods have a unique root, i.e. the minimization of the exergy losses, pinch analysis has evolved to become an instrument of direct and optimal design of a heat exchanger network while exergy analysis as such does not give an indication about process optimization. In combination with an adequate simulation code of a process, however, it can help to find the optimum process structure.
Exergy as an objective function to MINLP problems in process synthesis
Authors: Futterer Eberhard , Gruhn Günter , Lohe Bernd , Noronha Santosh , Rücker Andreas 
Published: August 2005

AbstractThe optimal layout of a chemical plant is determined by both economic and environmental aspects. The mathematical approach to this problem is given by representing the process through a superstructure, including any foreseeable process topology. It is described by integer variables, whereas real variables arise from the unit models and the thermodynamic calculations. By including process constraints and an objective function, a Mixed Integer Nonlinear Programming (MINLP) optimization problem is postulated. In this paper MINLP algorithms are combined with a technique for the exergy analysis of chemical processes for the preliminary screening of process alternatives. The exergy analysis as a screening technique is advantageous due to a significantly smaller amount of required data and computing time, compared with true optimization, including cost estimation at an earlier stage of process synthesis and analysis. Thus, a broader solution space can be examined. The subsequent cost analysis has then only to be focused on a reduced set of parameters.
Growth of a liquid film accompanied by a zero‐order reaction
Authors: Sirohi Vivek , Garg Rajeev , Bhaskarwar Ashok N. 
Published: August 2005

AbstractThe growth of a thin liquid film surrounded by gas pocket(s), undergoing absorption with a zero‐order chemical reaction, has been simulated by an apt mathematical model in order to study the influence of various parameters involved. The solution has been obtained semi analytically using Goodman's integral method and solving the resulting differential equation by a fourth‐order Runge‐Kutta numerical integration algorithm. The computations reveal the strong dependence of film growth on reaction rate, diffusivity, and molar volume whereas the effect of gas‐pocket volume and initial film thickness are moderate.
Application of parametric sensitivity to batch process safety: Theoretical and experimental studies
Authors: Alós Miguel A. , Zaldívar Jose M. , Strozzi Fernanda , Nomen Rosa , Sempere Julià 
Published: August 2005

AbstractThe generalised thermal parametric sensitivity criterion is applied to the thermal behaviour of the esterification of 2‐butanol with propionic anhydride in a batch reactor under isoperibolic conditions. The reaction is catalysed by sulphuric acid, and the study covered the effects of both catalyst concentration and, in the absence of catalyst, jacket temperature. The experimental location of regions of parametric sensitivity agreed well with theoretical predictions. However, the process conditions that meet conventional standards for safe process design fall into the supercritical sensitivity region of the parametric model. This apparently contradictory result is discussed. The usefulness of the parametric sensitivity approach is illustrated by practical examples of scale‐up and heat transfer in reactions prone to thermal runaway.
Hybrid knowledge‐based tool for mixing equipment selection – the fuzzy neural network
Authors: Kraslawski Andrzej , Pedrycz Witold , Koiranen Tuomas , Nyström Lars 
Published: August 2005

AbstractThe hybrid knowledge‐based system proposed in this paper consists of a “stiff” segment, viz. the expert system based on the object‐oriented approach, and a flexible part, viz. the neural network. Some of the input parameters of the problem and output parameters of the “stiff” system are presented as the fuzzy numbers. Detailed information is also presented about the development of the neural network. The most evident advantages of the proposed introduction of a hybrid architecture of the knowledge‐based system are a faster evaluation and generation of design alternatives and support of systematic searches and storage of experience. In addition, the resulting ability to extrapolate results would be unattainable with separately acting stiff and flexible systems. A system for the estimation of the parameters of a mixing system for wastewater treatment is presented as an example to illustrate the principles of the hybrid system.
Freezing time predictions of buried pipes: A 3‐D transient simulation
Authors: Hastaoglu Mehmet A. , Hakim Ali Abbas 
Published: August 2005

AbstractHeat transfer from a buried pipe carrying a flowing liquid is analysed using a 3‐dimensional geometry, transient modeling and numerical methods. The pipe is buried horizontally in soil whose initial surface temperature is assumed to be below that of the bulk soil and the pipe, and also below the freezing temperature of the liquid. The problem is solved using string‐intersected‐boundaries and a three‐level alternating‐direction‐implicit finite‐difference method. It is possible to predict the time taken for the fluid anywhere in the pipe to fall to its freezing point. The minimum burial depth needed so that the pipe does not freeze is also predicted. The simulation was run on an ordinary mainframe computer with very small computation times. The package developed can be used by designers such as pipeline, plant and water distribution engineers.