bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extraction of zinc by alkyl thiophosphoric acids with emulsion liquid membranes
Authors: Vasconcelos Jorge M. T. , Carvalho Jorge M. R. 
Published: August 2005

AbstractTreatment of a given multicomponent cationic mixture was studied applying the emulsion liquid membrane (ELM) separation technique for Zn recovery. Experimental apparatus and conditions are described. Comparative studies using two zinc‐selective ion exchangers (thio‐DEHPA and dithio‐DEHPA) were carried out whereby the composition of the liquid membrane and the operating conditions were investigated for both extractants. A useful method of representing the concentrations of the feed and the receiving aqueous phase is proposed, which allows the occurrence of break‐up and/or osmosis to be easily detected.
Pellet heat transfer coefficients in packed beds: Global and local values
Authors: Wijngaarden Ruud J. , Westerterp K. Roel 
Published: August 2005

AbstractPellet heat transfer coefficients in a packed bed have been obtained, both for specific individual pellets and for the entire bed. They are referred to as local and global values, respectively. It appears that the local values are scattered around the global value. This is due to the heat transfer coefficient of individual pellets being statistically distributed, as a result of the randomnes of the packing. At low Reynolds numbers, both global and local values fall well below Nu = 2, which is the lower limit for a single sphere in absence of convection. In the literature, this behaviour has been attributed i.a. to axial dispersion and fluid maldistribution. However, these phenomena cannot explain why the same behaviour is observed in slurries. The fact that the local values fall below Nu = 2 would suggest that neither of these explanations is valid for packed beds.
Investigations on hydrodynamics of radial flow moving bed reactors
Authors: Song Xuqi , Wang Zhanwen , Jin Yong , Gong Meishan 
Published: August 2005

AbstractDistributions of pressure and velocity in the main channels were studied in a radial flow cold model of a moving bed reactor, 500 mm in diameter, in four different gas flow modes, inward Z gas flow, inward Π gas flow, outward Z gas flow, outward Π gas flow. It has been found that, in outward Π gas flow mode, the axial non‐uniformity of the gas is at a minimum. The following correlations are proposed for the momentum recovery factors Ka and Kb: Ka = 0.684 + 0.0128 (du/dx)/u, Kb = 1.135 + 0.0158 (du/dx)/u. Pressure distributions in the main channels can be accurately predicted using Ka and Kb.
Distribution of energy dissipation rate in an agitated gas‐liquid system
Authors: Fořt Ivan , Machoň Václav , Kadlec Petr 
Published: August 2005

AbstractThis contribution presents a theoretical description of the relationship between the rate of energy dissipation per unit volume and the mean kinetic energy of turbulence per unit volume in a mechanically agitated gas‐liquid system. For agitated systems with standard (Rushton) turbine impellers, the effect of the aeration rate on the distribution of the rate of energy dissipation per unit volume in the system was investigated. It follows from the experiments carried out that the gas flow rate significantly affects the rate of energy dissipation per unit volume in the impeller region as well as in the bulk of the agitated batch. In the impeller region, the investigated rate of energy dissipation markedly increases with increasing gas flow rate and, in the remaining part of the agitated batch, it decreases. Moreover, the rate of energy dissipation near the impeller depends strongly on the local gas hold‐up which corresponds to the regime of two‐phase flow behind the impeller blades (i.e. to the occurrence of clinging of ragged cavities).
Correlation and prediction of gas solubility in heavy complex liquids
Authors: Mandagarán Beatriz A. , Campanella Enrique A. 
Published: August 2005

AbstractA lattice‐gas model is used for calculating the solubilities of light gases in heavy complex hydrocarbons. For waxes, the model gives a good prediction of the solubilities on using the molecular weight of the liquid to describe the solvent. For crude oils and coal‐derived liquids, the prediction is of only modest quality. However, it does improve on using experimental Henry's constants.
Reactive liquid‐liquid test system Zn/Di (2‐ethyl hexyl) phosphoric acid/n‐Dodecane. Equilibrium and kinetics
Authors: Wachter Bruno , Bart Hans‐Jörg , Moosbrugger Thomas , Marr Rolf 
Published: August 2005

AbstractThis contribution reviews the models for equilibrium and kinetics of the system Zn/D2EHPA/n‐dodecane (and other diluents), published during the past decade, as well as values of the appropriate model parameters, i.e. of equilibrium and reaction rate constants. The reviewed kinetic models comprise those for kinetic, diffusional and mixed mass transfer regimes. It is shown that, under certain conditions, the rate equation within the kinetic regime has the same mathematical structure as the equations for the overall mass transfer rate within the diffusional and mixed mass transfer regimes. This means that the same equation interprets experimental data from each of the three regimes. Thus, a fit of experimental data to a model is not sufficient for discriminating between the mass transfer regimes. Results of kinetic experiments, using a stirred mass transfer cell with constant interfacial area, are presented.
Hybrid modelling of yeast production processes – combination of a priori knowledge on different levels of sophistication
Authors: Schubert Jörg , Simutis Rimvydas , Dors Michael , Havlík Ivo , Lübbert Andreas 
Published: August 2005

AbstractProcess models are used to formulate knowledge about process behaviour. They are applied, e.g., to predict the process' future behaviour and for state estimation when reliable on‐line measuring techniques to monitor the key variables of the process are not available. There are different sources of information available for modelling, which provide process knowledge in different representations. Some elements or aspects may be described by physically based mathematical models and others by heuristically obtained rules of thumb, while some information may still be hidden in the process data recorded during previous runs of the process. Heuristic rules are conveniently processed with fuzzy expert systems, while artificial neural networks present themselves as a powerful tool for uncovering the information within the process data without the need to transform the information into one of the other representations. Artificial neural networks and fuzzy technology are increasingly being employed for modelling biotechnological processes, thus extending the traditional way of process modelling by mathematical equations. However, a sufficiently comprehensive combination of all these techniques has not yet been put forward. Here, we present a simple way of combining all the available knowledge relating to a given process. In a case study, we demonstrate the development of a hybrid model for state estimation and prediction on the example of a yeast production process. The model was validated during a cultivation performed in a standard pilot‐scale fermenter.
Removal of ethoxylated aliphatic amines from zinc containing effluents by adsorption on macroporous resins
Authors: Heitzsch Olaf , Stephan Holger , Gloe Karsten , Mühl Peter , Hellmig Reinhard 
Published: August 2005

AbstractThe separation of ethoxylated aliphatic amines from zinc containing effluents with macroporous polymeric adsorbents Wofatit EP 61, EP 62, Y 59, Y 77 and active carbons has been examined. The adsorption behaviour has been investigated as a function of temperature, time and concentration of Na2SO4, ZnSO4 and H2SO4. The macroporous polymers EP 61, Y 77 and Y 59 are capable of separating ethoxylated aliphatic amines from effluents of viscose fibre industry at higher temperatures and under weakly acidic conditions. In contrast to active carbon, inorganic components are not adsorbed on the investigated macroporous resins. Data obtained in a concentration range of 0 to 10 g of adsorbate per litre produced a Langmuir profile for adsorption of ethoxylated aliphatic amines by polymeric adsorbents.
Catalytic dehydrogenation of methanol to water‐free formaldehyde
Authors: Su Shoujin , Zaza Philippe , Renken Albert 
Published: August 2005

AbstractCatalytic dehydrogenation of methanol is a promising process of producing water‐free formaldehyde. The present paper reviews research in this field. As effective catalysts mainly transition metal compounds as well as oxides and salts containing sodium have been reported. Several catalysts exhibit high activity and high selectivity, for formaldehyde at low conversions while further efforts have to be made to improve catalyst stability and selectivity at high conversions. Catalytic dehydrogenation of methanol to formaldehyde is compared with methanol oxidation.
Supported nickel catalyst from hydroxycarbonate of nickel and aluminium
Authors: Rathouský Jiří , Schulz‐Ekloff Günter , Stárek Jindřich , Zukal Arnošt 
Published: August 2005

AbstractThe hydroxycarbonate of nickel and aluminium (Ni/ Al = 3) with a hydrotalcite‐like structure is an outstanding precursor of the active component of supported nickel catalysts. Good mechanical strength and suitable nickel content of these catalysts, which are necessary for practical applications, can be achieved by mechanical mixing of this compound with an additional support. The catalyst prepared from a mixture of 56.5 wt‐% of nickel‐aluminium hydroxycarbonate and 43.5 wt‐% of γ‐alumina was proven to have a stable catalytic activity in the methanation reaction at 2 MPa and 800 K.
Further remarks on the linear relationship between stoichiometry and dimensional analysis
Authors: Pethö Árpád 
Published: August 2005

AbstractThe phrase “further remarks” in the title of this short paper is meant to imply that reactions and dimensionless groups are not only purely algebraic concepts, but definite numerical values can also be associated with them; in stoichiometry this evaluation may relate, for example, to the heat of reaction and, in dimensional analysis, to what is called a dimensionless number. On the basis of the evaluation concept, it will be shown that a counterpart of Hess' law in thermochemistry is valid in dimensional analysis.
Non‐Darcian non‐isothermal compressible flow and heat transfer in cylindrical packed beds
Authors: Foumeny Esmail A. , Ma Jian 
Published: August 2005

AbstractKnowledge of transport processes is of considerable practical importance in the design and performance evaluation of packed bed reactor systems. Acquisition of the required information necessitates a realistic mathematical description of the system. In this study, numerical analysis is performed for forced convective non‐Darcian, non‐isothermal compressible flow and heat transfer in cylindrical packed beds. Local structural and transport properties are considered. The influence of compressional work as well as viscous dissipation on the thermal field is evaluated and a general criterion provided for assessing the effect of expansion.
A new design concept of structured packing column auxiliaries
Authors: Spekuljak Zvonko , Monella Horacio 
Published: August 2005

AbstractThis paper discusses the criteria for obtaining an improved performance of structured packing columns in gas‐liquid contacting, by improving the liquid and gas distributors. A new liquid distributor design, specific for structured packing columns is presented. Experimental measurements which quantify the improvements attained by the new distributor are also presented. Furthermore, gas flow distribution requirements for structured packing columns are discussed. Three “case studies” indicative of the implementation of the proposed distributor concept in industrial columns are included. Case (a) CO2/MEA removal column, case (b) ammonia splitter and case (c) acid gas neutralization column.
Air purification by catalytic oxidation in a reactor with periodic flow reversal
Authors: Van De Beld Bert , Westerterp K. Roel 
Published: August 2005

AbstractThe behaviour of an adiabatic packed bed reactor with periodic flow reversal has been studied by means of model calculations. A heterogeneous model as well as a pseudo‐homogeneous model have been developed. It is shown that a high degree of conversion can be obtained in an autothermal process even with very low adiabatic temperature rises of some 10 to 20 K. The reactor is insensitive to fluctuations in inlet concentrations and in through‐put. Short‐cut methods proposed in the literature for calculating the plateau temperature in the pseudo‐steady state are studied. The so called countercurrent‐flow reactor approach showed reasonable agreement with the plateau temperature obtained by dynamic calculations with the full reactor model.
Mixing of large volume gas flows in pipes and ducts. Visualization of concentration profiles
Authors: Fellhölter André , Mewes Dieter 
Published: August 2005

AbstractConcentration profiles are measured during the mixing process of carbon dioxide and air, which were injected into the rectangular cross section of a duct. The volume flow rates of both components differ considerably. The non‐stationary and three‐dimensional concentration fields are measured by optical tomography using holographic interferometry as the measuring principle. Projection data from four different viewing angles are used for tomographic reconstruction by the ART method. Pressure losses due to mixing processes are also measured. Results are presented for different angles of injection and different ratios of momentum flow rate for single and multiple jets of carbon dioxide which were injected into the carrier gas stream of air.
Development of a mathematical model for a secondary reformer
Authors: Raghunandanan Kunduvelil S. , Reddy Kandi Venkat 
Published: August 2005

AbstractA rigorous one‐dimensional heterogeneous model is developed for a secondary reformer in an ammonia plant with special emphasis on the catalyst particle models. These are based on the effective diffusivity model and the Stefan‐Maxwell model in the catalyst pore and the film around the catalyst particle. The performance of these four models is evaluated for the data collected from a commercial reformer in the complete operating range and recommendations are made regarding the use of appropriate particle models. The models for the catalyst particle show considerable deviations at the particle level but the reformer simulations produce almost identical results at the global level for all the four particle models. The need for a rigorous treatment of interphase resistance to mass transfer has been clearly demonstrated by comparison of the present model with the model of Singh and Saraf.
Comparison of the single‐bubble‐class and modified two‐bubble‐class models of bubble column reactors
Authors: Modak Shrikant Yadneshwar , Juvekar Vinay Anant , Rane Vishwanath Chango 
Published: August 2005

AbstractGas phase conversions and product selectivities predicted by the single‐bubble‐class and modified two‐bubble‐class models of bubble column reactors are compared for a multistep gas‐liquid reaction involving series/parallel steps. A situation is considered where the first reaction step is fast and occurs in the interfacial region while the other reaction steps are slow and occur only in the liquid bulk. Equivalent hydrodynamic and transport parameters provide a common basis for the comparison. The differences in the gas phase conversions predicted by these models are insignificant. However, the two models predict very different values of selectivities for the intermediate products. This analysis enables us to judge the range of applicability of the single‐bubble‐class model in design and scale‐up of bubble column reactors.
Single and multicomponent adsorption equilibria of carbon dioxide, nitrogen, carbon monoxide and methane in hydrogen purification processes
Authors: Sievers Werner , Mersmann Alfons 
Published: August 2005

AbstractSingle, binary, ternary and quaternary adsorption equilibria of CO2, CO, CH4 and N2 on molecular sieve 5A and activated carbon were experimentally determined over a pressure range from 10−4 to 101 MPa, a temperature range from 303 to 363 K and at various compositions. The adsorption equilibria of steam reformer gases as needed for the hydrogen purification in pressure swing adsorption units were measured by using a circulating volumetric method. For the temperature‐dependent correlation of pure gas isotherm fields the Toth equation, which is a favorable model for heterogeneous adsorbents, was extended by two parameters accounting for the temperature‐dependencies of the saturation loading and the heterogeneity parameter. Multicomponent equilibria were successfully predicted from single component isotherms by the Ideal Adsorbed Solution Theory based on the accurate representation of the pure component data by this temperature dependent Toth equation. Other thermodynamic models like the HIAS, the MIAS, the SPD or the VS theory and the Statistical Thermodynamics Model were also applied to the prediction of the adsorption equilibrium and the temperature and pressure dependence of the selectivity, with comparable success, which is due to the quasi‐ideal adsorption behavior even at a high pressure.
Dynamic response and safety assessment of a batch process on cooling breakdown
Authors: Koufopanos Charalambos A. , Karetsou Ageliki , Papayannakos Nikos G. 
Published: August 2005

AbstractCooling breakdown in highly exothermic reaction processes may lead to runaway. The sensitivity and the safety assessment of a batch process on cooling breakdown are studied. The dependence of the minimum cooling time and the maximum allowable time of cooling breakdown for safe operation on the process parameters is investigated.
Continuous fermentation with product recovery by in‐situ extraction
Authors: Weilnhammer Christian , Blass Eckhart 
Published: August 2005

AbstractThe productivity of fermentations is often limited by end product inhibition. This can be avoided by continuous removal of the inhibiting product from the broth. Such in‐situ separation can be conveniently accomplished by liquid‐liquid extraction. As an example, the continuous fermentation of ethanol by the thermophilic, anaerobic bacterium Clostridium thermohydrosulfuricum is investigated in a 20‐1 fermenter with simultaneous in‐situ extraction by oleyl alcohol as organic solvent. Continuous fermentations with and without in‐situextraction were carried out with systematic variation of the independent operating conditions, viz. feed glucose concentration, broth flow rate and solvent flow rate. The experimental results of 18 steady states are reported. They show that in‐situ extractions doubles the yield, selectivity and space‐time yield of ethanol in comparison to fermentations without in‐situ extraction. A biomodel elucidates the influence of feed glucose concentration, broth flow rate and solvent flow rate on the productivity of the fermentation process. Finally, a cost model was developed for the investigated fermentation which allows economic evaluation of the results of experiments and simulation. A sensitivity study elucidates the economic limits and advantages of fermentation with in‐situ extraction compared to a common fermentation without product separation.
Concept of a sterile concentration process for milk by multistage flash evaporation
Authors: Kiesner Christian , Eggers Rudolf 
Published: August 2005

AbstractIn the proposed combined sterilisation and concentration method, the original milk is first sterilised under conditions of continuous flow and after reaching the desired sterilisation temperature the product is concentrated by means of flash evaporation during subsequent cooling. Addition of stabilisers to maintain the thermal stability of the concentrate during sterilisation is not necessary in this process. The method presupposes that cooling with concentration is carried out under sterile conditions. This is technically quite feasible on use of multistage flash evaporation.
Temperature oscillation calorimetry in stirred tank reactors with variable heat transfer
Authors: Carloff Rüdiger , Proß Alexander , Reichert Karl‐Heinz 
Published: August 2005

AbstractA new method for applying reaction calorimetry to stirred tank reactors with variable heat transfer is presented. Sinusoidal temperature oscillations are induced by an electrical heater placed either in the reactor or in the jacket in order to decouple the chemical heat production from the variable heat transfer during reaction. Multiplication of the reactor heat balance by periodic functions and integration yields the overall heat transfer. Temperature oscillation calorimetry was successfully applied to the free radical polymerization of methyl methacrylate in ethyl acetate which shows a strong decrease in heat transfer.
Design of a packed column for ethanol extraction. Equilibrium and kinetics studies
Authors: Ismael R. Costa , De Carvalho J. M. Rodrigues , Dias S. M. Martins , Novais J. Maggiolly 
Published: August 2005

AbstractComputer‐aided design of a packed column to remove ethanol from aqueous solution with dibutyl butylphosphonate (DBBP) was accomplished with a programme based on the Pratt method and on the slip velocity equation. Reliable data for successful computation were obtained from literature correlations (drop size, hold‐up and axial mixing coefficients for different types of packing) and from experimental work (equilibria and kinetics). Equilibrium studies on the H2O‐ethanol‐dibutyl butylphosphonate system were performed at different temperatures. A decrease in temperature increased the selectivity of the extractant while the distribution coefficient of ethanol, KD ≈ 1.0, remained constant. The behaviour of the system kinetics towards temperature is assessed in order to determine the initial mass transfer flux (892 × 10−3 kg m−2s−1, 30°C) and the activation energy, 22.9 kJ/kmol. The process is governed by the diffusion of the species involved. The influence of the type of packing of the column on its design is analyzed from the inventory volume of the solvent, the total volume of the column and the axial dispersion coefficients under normalised inlet and outlet conditions.
New technology for hydrogen production by the catalytic oxidation and steam reforming of methanol at low temperatures
Authors: Trimm David L. , Wainwright Mark S. 
Published: August 2005

AbstractA simple design of an adiabatic reactor for the production of hydrogen from methanol without external heating has been explored. Heat and steam are generated by oxidising part of the methanol and are removed in the process of reforming methanol to hydrogen. The reactor design emphasises the degree of control that can be achieved in a two‐bed system by controlling the air to methanol and water to methanol ratios in the feed. Predictions of the model are compared with experimental testing to allow optimisation of the process. Up to 75% of methanol can be converted to hydrogen.
Basic sites on the surface of oxide catalysts responsible for oxidative methane coupling
Authors: Davydov Anatolii Aleksandrovich 
Published: August 2005

AbstractThe basic sites of various oxide catalysts for the oxidative dimerisation of methane were studied by FTIR spectroscopy of adsorbed molecular probes (chloroform and CO2). The methods used are compared and the advantage of CO2 as probe for specifying the basic sites is demonstrated. The strengths of the basic sites were seen to correlate with the spectral parameters of the surface carbonates. Differences in spectral responses of carbonates are attributed to the different states of oxygen participating in their formation. The concentration of the strongest sites was estimated. A study of the catalytic activity of this system indicates that the system's activity in oxidative methane coupling depends on the presence and concentration of strong basic sites on the catalyst surface.