bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heavy metal recovery by extraction and permeation in incineration preocesses
Authors: Bart Hans‐Jörg , Marr Rolf , Draxler Josef , Hartl Josef 
Published: August 2005

AbstractIncineration processes are critical for the environment. SO2 and NOX removal with processes is nowadays commonplace. Up to now, heavy metal were recovered via precipitation. The alternative use of liquid ion exchange techniques offers an easy re‐use of the heavy metals, which are obtained as concentrates. A separation process is described, starting from laboratory experiments and ending with pilot plant field tests. A cost comparison for extraction, permeation and precipitation gives the scope of the necessary expenses for such environmentally controlled processes.
Modeling and simulation of reactions involving bifunctional catalysts
Authors: Schäfer Harald A. , Hoefer Eberhard P. 
Published: August 2005

AbstractA mathematical model based on experimental results is set up for a typical model reaction of hydrocarbon reforming, namely the dehydroisomerization of methyl cyclopentane. Computer simulations shows that the existing theory about the reaction path of hydrocracking reactions involving bifunctional catalysts may be only partly valid.
Inertial deposition on front and rear sides of ribbons at intermediate and high reynolds numbers
Authors: Dau Günter 
Published: August 2005

AbstractDeposition of particles from gas flows on ribbons in normally expected on the front side. Collision efficiencies of ribbons are presented for this case, obtained by means of single particle trajectory computation, which is based on numerically determined flow fields in the Reynolds number range between 2 and 50 and on the potential flow model. Further, it is shown, that deposition of particles on the rear side can be caused by eddylike motion of the fluid in the wake of the ribbon. For this to occur, two conditions must be fulfilled: the free shear layer between the wake and the outer flow must be turbulent to cause lateral transfer of particles into the wake and the Stokes number may not exceed 0.5.
The linear relationship between stoichiometry and dimensional analysis
Authors: Pethö Árpád 
Published: August 2005

AbstractThe linear algebraic character of the formal representation of chemical species and their reactions is compared with the procedure of searching for dimensionless numbers in a set of physical quantities. A straightforward algorithm is presented to find a finite set of solutions to the relevant system of “balance equations”, the so‐called minimal (or simple) solutions. At the third stage of the hierarchy thus established, “mechanisms” among reactions as well as “representations” among dimensionless group can also be defined.
Anodic dehalogenation of 1,2‐dichloroethane in aqueous electrolytes
Authors: Beck Fritz , Schulz Harry , Wermeckes Bernd 
Published: August 2005

AbstractA solution of 0.1 M 1,2‐dichloroethane in 1 M H2SO4 was anodically converted to CO2, Cl2 and HCIO4 as the main products at smooth platinum. The current efficiency for CO2 exceeds 60% at low current densities, while HClO4 is obtained with about 20% current efficiency. Chlorinated products such as 1,2′,2‐trichloroethane are formed in negligible amounts. Platinum plays a distinctive role as anode material and shows a reaction limited anodic prewave. Our experimental findings lead to a mechanism, whereby DCE is initially hydroxylated to form chloroacetaldehyde chlorohydrin which releases HCl and becomes rapidly further oxidized to monochloroacetic acid. The cleavage of the CC bond proceeds via its anodic decarboxylation. Possible practical applications in the field of anodic water purification and in the direct electrosynthesis of vinyl chloride are discussed.
Some strategies for the kinetic study of complex heterogeneous catalytic reactions
Authors: Xu Jianguo , Hoffmann Ulrich 
Published: August 2005

AbstractThis paper presents a method of transforming the non‐liner regression problem in the kinetic study of complex heterogeneous catalytic reactions into a linear regression problem. Application of this method reduced the number of parameters to be estimated by n‐1, where n is the number of independent reactions. In addition, a stepwise model discrimination strategy in introduced to reduce the number of equation sets ad equations in the set undergoing parameter estimation. These two new approaches are very advantageous in reducing the computation effort, especially when the number of independent reactions is large. The linear regression method and the stepwise model discrimination strategy are successfully applied in the kinetic study of the methanol synthesis system in which the formation rates of methanol, methane, ethanol and ethane are considered.
The Markov process approach to modelling of residence of time distributions in flow systems
Authors: Kumar Surendra , Pethö Árpád 
Published: August 2005

AbstractThe Markov process approach, as used in the modelling of particle residence time distribution in a flow system of interlinked compartments, has been compared with the deterministic model of a complex reaction system of the first order. In the latter model, interfacial reactions take place between flowing phases, corresponding to the compartments in the stochastic model. It has been demonstrated that the two approaches are equivalent. A direct method of calculating the higher moments of the residence time distribution has been verified.
Effect of dispersions of CSD in continuous MSMPR crystallizers
Authors: Gupta Bhaskar Sen , Dutta Tapas K. 
Published: August 2005

AbstractA general model is proposed to predict the crystal size distribution from multistage MSMPR Crystallizers taking into account shape factor, birth size and growth rate dispersions. Two cases, namely nucleation in the first crystallizer and the same process in all crystallizers have been considered. The developed equations can be solved easily by the Monte Carlo technique. The model represents an extension of the earlier work of Sen Gupta and Dutta.
Drop coalescence on inclined plates in liquids
Authors: Meon Walter , Blass Eckhart 
Published: August 2005

AbstractInclined plates are often installed as mechanical separation aids in gravity settlers for the separation of liquid‐liquid systems. The authors investigated the process of coalescence of single drops on trickling films flowing off inclined plates. The method of investigation was developed by Blass and Rautenberg. It ensures that, under certain conditions, only hydrodynamic parameters influence the coalescence process to any significant extent. The coalescence time of the drops characterizes the process of coalescence. Short time between 1 and 3 seconds provide favourable conditions for coalescence whereas long times, often ten times as long or even longer are unfavourable. This contribution introduces a criterion for clear demarcation between these two ranges and also a determination of separation parameters for favourable conditions for coalescence. Furthermore, the function of the plates is described, which is determined by hydrodynamic and wetting processes. The characteristic operating regions of a plate are shown in a working diagram.
An improved SRK‐equation for the estimation of concentrations by inferential measurements
Authors: Karlström Anders 
Published: August 2005

AbstractA method is proposed for solving the vapour‐liquid equilibrium problem in binary distillation processes, when pressure and temperature are known. Special attention is paid to the applicability of the method for control purposes. Therefore, a comparison between measured and estimated concentrations is included for the case of propane‐propylene distillation. The method is based on an improved Soave‐Redlich‐Kwong equation of state and is easy to implement on a process computer. It yields a close approximation of experimental vapour and liquid volumes. On applying the original SRK‐equation at high pressures, an error in excess of 20% is obtained in the liquid volume which is one of the reasons why this equation cannot be used for control where high accuracy is required. In addition, the conventional mixing rule cannot reproduce the mole fractions correctly. Therefore, a new density‐dependent mixing rule is put forward for modelling of experimental results.
Apparatus for steady‐state kinetic measurements of the catalytic reduction of nitric oxide by ammonia on iron oxide
Authors: Claußen Michael , Kainer Hartmut , Kunz Ulrich , Hoffmann Ulrich 
Published: August 2005

AbstractThe reduction of nitric oxide with ammonia on an unsupported iron oxide catalyst has been studied in a continuous‐flow recycle reactor using simulated flue gas. The responses of the employed reactor system to step and pulse inputs of tracer indicate that the system could be regarded as a continuous stirred tank reactor (CSTR). Preliminary tests were carried out to determine the effect of temperature and particle size on the measured reaction rates. Additional experiments were performed in order to study the influence of oxygen and water concentration on these rates. A gas chromatographic system has been developed to analyze the gas components NO, N2O, NO2, NH3, H2O, O2, CO2 and N2. In addition, the concentrations of NO and NO2 were measured with a nondisperse infrared (NDUV/NDIR) analyzer.
Effects of sudden pressure changes in the surrounding gas phase on flow properties of bulk solids
Authors: Wiese Norbert , Schwedes Jörg 
Published: August 2005

AbstractThe variation in the behaviour of bulk solids as a result of sudden pressure changes in the surrounding gas phase is of interest in the application of lock hoppers for transfer of bulk solids into pressure vessels. By using such sluice systems, problems occur due to consolidation of the pressurized bulk solids. This paper presents the results of experimental and theoretical research, which allow to describe the influence of several parameters on pressure compensation and the degree of consolidation. With reference to the forces and mechanisms responsible for consolidation, it is possible to describe the different consolidation behaviour of incompressible (limestone) and compressible (hard coal) bulk solids.
Flow characteristics of large oscillating drops in liquid‐liquid systems
Authors: Al‐Hassan Tariq , Mumford Clive James , Jeffreys Geoffrey Vaughan 
Published: August 2005

AbstractA study was made of the flow characteristics of large oscillating drops of pure liquid‐liquid systems, using a thermostatically‐controlled, rising drop column, 50 mm in diameter and 1000 mm in length. Mirrors in the jacket enabled front and side views of drops to be photographed simultaneously. Single drops in the size range 5–10 mm were investigated with both mutually‐saturated phases and when the solute was being transferred from the dispersed phase. The systems studied were (1) toluene and acetone (dispersed)‐water (continuous), and (2) n‐heptane and acetone (dispersed)‐water (continuous). Acetone concentrations were varied up to 3.75 kmol/m3. The oscillations of a travelling drop were asymmetrical; therefore, the amplitude cannot be expressed accurately in terms of only two axes. The area change of the drop compared to that of a sphere of equal volume ‘ε’, was shown to represent the amplitude accurately. The periods of droplet oscillation were uniform for the mutually saturated systems of constant physical and flow properties but changed when mass transfer was taking place. The interfacial tension exerted a marked effect on the amplitude, which also depended upon the oscillation frequency. The amplitude changed with droplet size in a similar manner to the terminal velocity, i.e. it increased with increasing size until it reached a maximum, subsequently decreasing less rapidly. The drag coefficient increased with increasing rate of mass transfer from the drop. Correlation of the results and the area eccentricity ‘ε’ by dimensional analysis embracing all possible parameters and physical properties affecting drop oscillation, resulted in the correlation ε = 0.22 Sr0.42 We−0.53 M0.13 with a mean deviation of ± 14%. This will facilitate more accurate prediction of the interfacial area for mass transfer calculations, relating to equipment containing droplets in the oscillating regime.
Decrease of diffusion coefficients near binodal states of liquid‐liquid systems
Authors: Hampe Manfred Josef , Schermuly Wolfgang , Blaß Eckhart 
Published: August 2005

AbstractThis work investigates the thermodynamically based assumption that diffusion at binodal states of unstable fluid systems vanishes. It is shown experimentally that a scaling law, which describes the fall in diffusion near critical points, may also be applied in an extended form to its abatement at the limits of solubility. These results may profoundly affect the modelling of mass transfer between phases whose bulks exhibit states of saturation.
Operation data of a directly fired absorption heating unit with periodically operating absorber
Authors: Knoche Karl‐Friedrich , Seitz Carl‐Werner , Zerres Hilarius 
Published: August 2005

AbstractThis contribution presents the layout, construction, and experimental investigation of operation behaviour of a directly fired absorption heating unit with periodically operating absorber. The working system is CH3OH‐LiBr/LiOH. The unit is designed to generate a maximum heat load of 10 kW. The field of application is mainly in domestic heatIng. A special feature of the absorption heating unit is the provision of the major part of required process heat in the heat pump mode of operation with high efficiency. At extremely low ambient air temperatures, heat is supplied in the direct mode. A numerical simulation routine is also described. The simulation program describes both steady‐state and dynamic processes in the unit. With models for each component, the performance of individual components can be studied and optimized. The results presented here consist of the first experimentally obtained efficiencies in direct heating mode, results of numerical simulation of the component generator, and a comparison of measured and predicted characteristic system temperatures.
Adaptive pole removal control for a batch polymerization reactor
Authors: Wang Feng‐Sheng , Lin Yunng‐Chin 
Published: August 2005

AbstractA systematic method of controller design is introduced to determine the overall charcteristic behaviour developed on process pole removal. The time delay compensation is automatically incorporated in the proposed control law. The implemented tuning parameters in the law are confined to the range between 0 and 1 to guarantee the stability of the overall control system. Subsequently, the fixed and adaptive control strategies are implemented to simulate a batch PVC reaction system. The adaptive control scheme provides good, roubust control of this simulated reactor notwithstanding the wide range of operating conditions and non‐linear dynamics of the system. However, the fixed control scheme performs well only for a noise‐free system. In addition, two limiting control laws, derived from the proposed method, are also used to simulate the reactor. The results indicate that these laws are not suitable for this non‐linear reaction system.
Cocurrent vacuum de‐aeration of water for injection into oil reservoirs
Authors: Lydersen Aksel L. 
Published: August 2005

AbstractConventional vacuum stripping to reduce the oxygen content of injection water for secondary recovery of oil is carried out in packed columns with the released gases and water flowing countercurrently; hence large column diameters (normal liquid load circa 100 m3/(m2h)) and foaming that requires the addition of defoaming agents. Measurements with cocurrent and countercurrent flow at the same flow rate produced practically identical mass transfer coefficients. With flooding excluded in cocurrent flow, columns can be operated with higher liquid loads than in countercurrent flow. In addition, nitrogen released in the top part of the packing is better utilized as stripping gas, and foam is withdrawn as soon as it increases the pressure drop.
Electrochemical impedance spectroscopy of oxygen and hydrogen evolution on amorphous alloys in 1 M KOH
Authors: Kessler Teresita , Vilche Jorge R. , Ebert Michael , Jüttner Klaus , Lorenz Wolfgang J. 
Published: August 2005

AbstractThe mechanisms of oxygen and hydrogen evolution on amorphous alloys G 14 (Fe60Co20Si10B10) and G 16 (Co50Ni25Si15B10) in 1 M KOH at T = 298 K and 333 K were studied by electrochemical impedance spectroscopy (EIS). Comparative measurements were carried out on polycrystalline Pt electrodes. Impedance spectra in the frequency range 10−3 Hz ≤ f ≤ 104 Hz were analyzed to determine the kinetic behaviour of amorphous alloys by application of transfer function analysis, using non‐linear fit routines. The EIS‐data are interpreted in terms of consecutive reaction mechanisms for both oxygen and hydrogen evolution.
Absorption of nitric oxide in dilute nitric acid
Authors: Weisweiler Werner , Eidam Klaus , Thiemann Michael , Scheibler Erich , Wiegand Karl Wilhelm 
Published: August 2005

AbstractThis paper presents laboratory‐scale measurements on the absorption of nitric oxide in dilute nitric acid. The NO concentration in the gas feed varied from 250 to 10 000 ppm. Nitrogen was used as carrier gas. The concentration of nitric acid was between 30 and 60 mass‐%. Temperature during the measurements was set at 25 °C. In order to determine mass flow rates, experiments were performed in a double‐stirred cell. This type of absorber has a defined gas/liquid interface as the mass transfer area. The liquid phase is introduced periodically and the gas phase continuously. A well‐known model was used to describe the phenomenon of NO absorption. Several balance equations were established and solved. The calculated mass transfer rates were compared with those obtained experimentally. The empirical and theoretical data are in satisfactory agreement.
Photosensitive materials for use in velocity profile measurements in the water phase of air‐water systems and in single phase liquid systems
Authors: Douglas Peter 
Published: August 2005

AbstractThose chemical and photochemical characteristics of a photochromic system which are necessary for successful application to flow visualization studies in water are identified. The properties of a number of photochromic and photosensitive systems are discussed, and critically examined, with regard to these requirements.
Simulation of a distillation column on an IBM PC, accounting for real behaviour of electrolyte solutions
Authors: Bosen André , Roth Manfred 
Published: August 2005

AbstractThis contribution demonstrates the possibility of using a thermodynamic description of electrolyte solutions directly for computer simulation of distillation columns. Coefficients are determined for a combination of a solvation model with a local composition equation for the activity coefficient. The use of one set of coefficients yields good results of calculation of vapour pressure, vapour phase composition and caloric data of hydrochloric acid. Solution of material and heat balance equations of distillation columns is achieved on an IBM PC with the above description. Two illustrative examples of an absorption and a rectification calculation are presented
Dynamic behaviour and simulation of a liquid‐liquid extraction column
Authors: Hufnagl Harry , McIntyre Michael , Blaß Eckhart 
Published: August 2005

AbstractDynamic behaviour of a stirred liquid‐liquid extraction column was studied experimentally. Various input variables of the column were varied stepwise and the resulting variations in the system and output variables were measured. In addition to experimental work, a computer model was developed on the basis of the dispersion model to simulate the dynamic behaviour of the extractor. This model forms a component program of the dynamic process simulator DIVA, developed at the TU Stuttgart. The experiments showed that the hydrodynamic parameters exhibit no significant dynamic behaviour of their own. Therefore, changes occurring in these parameters closely follow variations in input and system variables. As a result, steady‐state relationships for the calculation of flow parameters could be used in the simulation program. The simulator satisfactorily reproduced the experimental results for a number of disturbances. However, this was not always the case. As shown in the following, the model did not take into account the column level controller which, under certain conditions, exerts a very strong influence on the column's dynamic behaviour. As a result, larger differences occurred between experimental and simulated data. This influence on the extractor's dynamic behaviour can, however, be eliminated by a simple modification of the level controller arrangement.
Calculation methods for multicomponent adsorption equilibria
Authors: School Stephan , Schachtl Martin , Sievers Werner , Schweighart Peter , Mersmann Alfons 
Published: August 2005

AbstractThe knowledge of multicomponent adsorption equilibria is of great importance for the industrial design and application of adsorptive purification and separation processes. As the experimental determination of the required data is time‐consuming and costly, theoretical help is desirable. This contribution presents and assesses the most common theoretical approaches to the calculation of multicomponent adsorption equilibria. The models are based on the assumption of an adsorbed solution, extension of the volume filling of micropores theory or statistical thermodynamics. These models are applied to different adsorptive/adsorbent systems with ideal and non‐ideal equilibrium behaviour. It is established that, at low coverages of adsorbent surfaces, all theories provide good estimates of the adsorbed phase composition and total loading while, at high saturations, no model is completely satisfactory.
Simulation of fluidized‐bed reactors for catalytic oxidative coupling of methane to C2‐hydrocarbons
Authors: Mleczko Leslaw , Andorf Renato , Baerns Manfred 
Published: August 2005

AbstractThe “bubble assemblage model” of Kato and Wen was applied to simulate the catalytic oxidative coupling of methane to C2‐hydrocarbons in a fluidized bed reactor. Simulation results were compared to experimental data obtained in a laboratory‐scale fluidized bed reactor. To improve the accuracy of predictions, the influence of fluid bed hydrodynamic and kinetic submodels was investigated by applying a sensitivity analysis. It was shown that the most important element in the model is the applied reaction scheme; the consecutive reactions of C2 hydrocarbons occurring most probably in the gas phase should be considered.
Trichlorosilane chlorination in a multiphase multicomponent photoreactor
Authors: Schirmeister Reinhard , Hoffmann Ulrich 
Published: August 2005

AbstractThe photochemical reaction SiHCl3+Cl2→SiCl4+HCl is of industrial importance in the production of pure silicon for the semiconductor industry. The present paper deals with an experimental investigation of the kinetics of this purification step. The main reaction occurs in the liquid phase and is initiated by light. In this gas‐liquid reaction system, all components, which are present in both phases, were analyzed by gas chromatography. Reaction progress was monitored by recording the pressure rise. Apart from the influence of wavelength and radiation intensity on the above photoreaction, reactions in the absence of light and on the wall were also investigated.
Chemical reaction fouling of organic fluids
Authors: Watkinson A. Paul 
Published: August 2005

AbstractChemical reaction fouling of heat exchangers involves deposition that is caused by chemical reactions which occur in the fluid, or on the surface itself. The factors which influence fouling of organic fluids via autoxidation and thermal decomposition processes are described and the dependence of the rate of thermal fouling on chemical effects and process variables demonstrated. Mitigation techniques are outlined in brief.