bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystallization of potash alum in an MSMPR crystallizer
Authors: Synowiec P. , Sangl R. , Mersmann A. 
Published: August 2005

AbstractNew data are presented on the crystallization of potash alum (KAl(SO4)2·12H2O) from solution, in a continuously operating MSMPR cooling crystallizer, 61 in volume. Population density distributions were determined by sieve analysis. Highly polydispersed product was obtained, with median crystal size, L50, in the range between 264 and 607 μm. Suspension density was varied between mT = 7 and 98 kg/m3. The results were evaluated according to an attrition model and the obtained kinetic efficiency should be valid for other types of crystallizers.
Experimental validation of a packed bed distillation model
Authors: Karlström Anders , Breitholtz Claes 
Published: August 2005

AbstractA mathematical model of a packed bed distillation column is presented and applied to a binary system in a full scale industrial distillation column with structured packings. The model is reduced by orthogonal collocation to sets of ordinary differential and algebraic equations. A linearized large state space model is then obtained and further reduced by the optimal Hankel norm method in order to obtain a model of manageable size. The model is studied under three different operating conditions in order to cover the feasible operating ranges during the experiments. The experiments carried out with a monoethanolamine‐diethanolamine system show a good agreement with the model implying that a control design based on the model is satisfactory. It is also shown that the control configuration to be used can be easily analyzed by the model, since different input and output structures can be studied. Furthermore, models based on one‐film and two‐film theories are compared in the frequency domain and show that, due to its simplicity, the one‐film theory should be used in control design.
Local heat transfer and heat flux distributions in finned tube heat exchangers
Authors: Schüz Gerhard , Kottke Volker 
Published: August 2005

AbstractA detailed analysis of the effect of local heat transfer distributions, which were determined experimentally, on temperature distributions in the fins and in the fluid between two adjacent fins of finned tube heat exchangers is presented. The heat transfer distributions, obtained by a mass transfer technique, prove to be very inhomogeneous over the fin surface, leading to variable results for fin efficiency calculated by the conventional method. In addition, the effect of temperature variation in the fluid, which is usually neglected in fin analysis, is shown in many cases to exert a very strong influence on fin efficiency and total heat flux. For the optimization of fin designs, a combined analysis of local heat transfer, conduction resistance in the fin and temperature variation in the passage is indispensable.
Xanthan production in stirred tank fermenters: Oxygen transfer and scale‐up
Authors: Herbst Holger , Schumpe Adrian , Deckwer Wolf‐Dieter 
Published: August 2005

AbstractThe microbial polysaccharide xanthan was produced by cultivation of Xanthomonas campestris in four stirred tanks with volumes ranging from 0.072 to 3 m3. Many of the previously suggested correlations for the volumetric mass transfer coefficient described the present data very unsatisfactorily. When Rushton turbines were employed as stirrers, the experimental results agreed well with a correlation suggested by Kawase and Moo‐Young; for the more energy‐efficient INTERMIG impellers, this correlation was modified by a factor of three. Constant specific oxygen transfer rate was found to be the appropriate scale‐up criterion for constant space‐time yield and constant product quality, specifically, the molar mass which determines the viscosity yield.
Modelling of mass transfer phenomena of associated systems in packed distillation columns
Authors: Savkovic‐Stevanovic Jelenka 
Published: August 2005

AbstractMass transfer between liquid and vapour phases in packed distillation columns has been investigated by the two‐film theory for binary associated systems. The effects of association reaction in systems with the association of one component in both phases, taking into account a concentration‐dependent liquid‐phase association constant, were examined. The mass transfer coefficients are modelled, taking into account the association constant. The experiments were carried out at atmospheric pressure with acetic acid‐benzene and acetic acid‐toluene systems in a column packed with Rasching rings.
Comparison of single and double inert tracer fluctuation measurements in a continuous stirred tank
Authors: David René , André Christophe 
Published: August 2005

AbstractA comparison is made between two different methods using laser induced fluorescence spectroscopy for measuring local concentration fluctuations in the same stirred tank. The first method using a single inert fluorescent tracer yields a segregation index quite different from that determined by the second method, which requires two inert tracers, a fluorescent one and a fluorescence quencher. By recalling the theoretical background, it is demonstrated that the characteristic segregation indices should be equal for the experiments under consideration. According to the discussion, it is likely that the double tracer method gives more reliable results.
Targeting for CO2emissions for Total Sites
Authors: Linnhoff Bodo , Dhole Vikas R. 
Published: August 2005

AbstractThis paper describes an approach based on the concepts of Pinch Technology for Total Site targeting for fuel and power. If specific CO2emissions for fuel and power are known, the approach will also target for CO2emissions for any given site in the industry. The approach takes account of the trade‐offs between process fuel and steam, between steam, site fuel and cogeneration, and of fuel mix. A case study is described where an 18% reduction in global CO2emissions is possible through the correct use of these trade‐offs.
Fuzzy sets. Introduction to theory and applications in process engineering
Authors: Kraslawski Andrzej , Nyström Lars 
Published: August 2005

AbstractFuzziness is quite a different notion from probability. Probability describes the objective uncertainty obtained on the basis of a large number of observations. Fuzziness describes the uncertainity that has a subjective meaning. Fuzzy notions describe the degrees of possession of a given property. The popularity of fuzzy set theory in solving control problems results from its ability to treat some situations which are difficult to deal with by the classical control theory. Fuzzy sets are used to control ill‐defined, complex, non‐linear systems. There are two aspects of this phenomenon. The first aspect concerns the descriptive ability of fuzzy sets. The second important feature is the applicability of fuzzy sets to work with incomplete, contradictory and subjective information. Fuzzy set theory is becoming increasingly important tool in the new fast developing disciplines of artificial intelligence: expert systems and neural networks. It creates completely new opportunities for the application of fuzzy sets in chemical engineering.
Studies on parametric sensitivity and safe operation criteria of batch processes
Authors: Papayannakos Nikos G. , Koufopanos Charalambos A. , Karetsou Ageliki 
Published: August 2005

AbstractHeat accumulation in batch reactors may eventually lead to a temperature runaway. Critical values of process parameters were used to investigate process safety. Parameter sensitivity is discussed for a wide range of operating conditions. Two criteria for safe operation are presented, based on critical values of process parameters.
Conversion of ethanol over metal‐exchanged zeolites
Authors: Schulz Jürgen , Bandermann Friedhelm 
Published: August 2005

AbstractThe effects of metal exchange between zeolites and alkali metals (Li, Na, K; zeolite Y, ZSM‐5, T), alkaline earths (Mg, Ca, Sr, Ba; ZSM‐5), transition metals (La, Ce, Cr, Mn, Fe, Co, Ni, Pd, Cu, Zn; ZSM‐5) and aluminium (ZSM‐5) on the conversion of ethanol were studied. Activities of the catalysts and selectivities for ethene, C3+ olefins, paraffins and arenes strongly depended on the cation, chosen for the modification. Only ethene was formed by alkali exchanged zeolites, the most active being Li‐Y. This could be confirmed by a long‐term ageing test with Li‐Y pellets under semi‐industrial conditions. The exchange of ZSM‐5 with alkaline earths or transition metals permitted the formation of a wide variety of products, raning from high ethene to high aromatic yields. A correlation between certain product selectivities and electronegativity was only possible in a rough approximation.
A study of phase equilibria sensitivity in the 1,1,1‐trichloroethane–1,2‐dichloroethane separation by distillation
Authors: Quiroga Mónica E. , Campanella Enrique A. 
Published: August 2005

AbstractThe sensitivity of the plate number and reflux ratio to the description of vapour‐liquid equilibria in the 1,1,1‐trichloroethane–1,2‐dichloroethane separation was calculated via case studies. Published experimental data are not sufficiently accurate to satisfy an adequate overdesign of the distillation column. On the other hand, the data are suitable for the design of an extractive distillation.
Defect structure of metal oxides at high temperatures
Authors: Paladino Ombretta 
Published: August 2005

AbstractHigh temperature oxidation of some metals contained in special alloys has been studied. Defect models for pure an doped CoO and pure NiO were developed and fitted to electrical conductivity data. The models involve different kinds of theoretically possible complex defects with different numbers of vacancies and interstitials forming a cluster. Equilibrium constants for defects formation have been estimated using an algorithm based on the constrained variation method that allows fitting of data to implicit models involving errors in all the measured variables. Results indicate the presence of a significant concentration of complex defects in CoO at high temperatures, while confirming the rather small concentration of these defects in NiO.
Inertial impaction of aerosol particles on single and multiple spherical targets
Authors: Hähner Frank , Dau Günter , Ebert Fritz 
Published: August 2005

AbstractInertial deposition of aerosol droplets (diameter: 1–14 μm) on steel spheres (diameter: 3–9 mm) was investigated. Air velocity was varied between 7 and 28 m/s (corresponding sphere Reynolds numbers: 1400–17000). The impaction on single spheres as well as that on linear arrays of eight spheres was measured. Theoretical results, based on potential flow investigations were verified by single sphere experiments. Of special interest was the range of lower Stokes numbers, where the theoretically predicted limit of deposition cannot be verified. The experiments on sphere arrays were for the first time performed in the low Stokes number range. Deposition on the leading sphere, relative to that on the shielded spheres, exhibits a maximum in the high Stokes number range, but this changes drastically in the low Stokes number range. Here, maximum deposition can be found on the shielded spheres while the leading sphere shows a markedly lower deposition.
Continuous computer controlled production of formate dehydrogenase (FDH) and isolation on a pilot scale
Authors: Weuster‐Botz Dirk , Paschold Holger , Striegel Bernd , Gieren Holger , Kula Maria‐Regina , Wandrey Christian 
Published: August 2005

AbstractA continuous production process has been developed up to pilot scale (300 l) for FDH production with the methylotrophic yeast Candida boidinii. A high cell mass specific FDH activity (50 U/g) is achieved by process computer controlled supply of pure methanol to operate the reactor at an optimum methanol concentration of 10 g/l. The maximum FDH spacetime yield achievable with this process control involves a residence time of 7 h. The FDH space‐time yield (STY) and FDH concentration are a function of the oxygen transfer rate (OTR) of the fermenter (maximum STY = 255 U/(l h) at kLa = 870 l/h). For a reasonable compromise between high FDH space‐time yield and high FDH concentration, an optimum residence time is adjustable by regulating the supply of nutrient salt solution in relation to the OTR of the fermenter. On a pilot scale (200 l continuously stirred tank reactor) roughly 4 million U of FDH were produced within 10 days at a residence time of 14.3 h. Isolation of intracellular FDH enzyme was performed using extraction with an aqueous two‐phase system (PEG/K2HPO4). A technical product quality of 1.2 U/mg FDH was achieved without any chromatographic purification step.
Kinetics and mechanisms of reaction between carbon disulphide and morpholine in aqueous solutions
Authors: Alper Erdogan , Bouhamra Walid 
Published: August 2005

AbstractThe reaction in aqueous solutions between carbon disulphide and morpholine has been studied experimentally at 303 K using a conductimetric stopped‐flow technique. The observed pseudo‐first order rate constant does not vary linearly with amine concentration but follows the equation:

.This equation is compatible both with (i) zwitterion intermediate and (ii) single‐step termolecular reaction mechanisms which were previously proposed for the corresponding reactions of CO2 and COS. Values of rate constants kAm and kw at 303 K are also reported.
Reduction of diesel particulate emissions by catalytic filtration
Authors: Hoffmann Ulrich , Rieckmann Thomas 
Published: August 2005

AbstractSeveral kinds of diesel soot filters and filter materials of high melting points with eleven different catalytic coatings were prepared. They were calcined at a maximum temperature of 1000°C. The reaction rate and the kinetic parameters of the combustion of diesel soot were determined in a closed loop laboratory reactor. A packed bed of alumina particulates was the most active filter in soot combustion. Catalytic coatings with oxides of vanadium, copper or cerium accelerated the reaction. In each case the effect of the coating was dependent on specific interactions between the catalyst and the filter material. The manner of filtration and the nature of the soot filter are found to be more important for the overall result than the nature of the catalytic coating.
Reaction engineering simulations of a fluidized‐bed reactor for selective oxidation of fluorene to 9‐fluorenone
Authors: Mleczko Leslaw , Pannek Ulrich , Baerns Manfred 
Published: August 2005

AbstractThe catalytic oxidation of fluorene to 9‐fluorenone in a fluidized‐bed reactor was investigated by modeling of the reactor and simulation of its performance. The “Bubble Assemblage Model” of Kato and Wen, the “Bubbling Bed Model” of Kunii and Levenspiel and the “Countercurrent Backmixing Model” of Potter were applied. From a comparison of simulation results obtained by the various fluidized‐bed models and a fixed‐bed model conclusions were drawn about the influence of interphase mass transfer and gas backmixing on the conversion of fluorene and slectivity of 9‐fluorenone formation. Furthermore, the dependence of conversion and selectivity on temperature and hydrodynamic conditions was investigated. In particular, the implications of a change of hydrodynamic conditions for scale‐up were analysed. The highest yield of 9‐fluorenone predicted for a bench‐scale fluidized bed amounted to 88% (XF = 97%, SNON = 91%). This yield was lower than in a fixed‐bed reactor (YNON = 92%, XF = 99%, SNON = 93%). A further drop of the yield was predicted when scaling‐up from a bench‐scale reactor to a commercial size unit (YNON = 54%, XF = 86%, SNON = 63%).
Pyrolysis of propane at reflected shock‐wave temperatures from 1300 to 2700 K
Authors: Wami Emenike N. 
Published: August 2005

AbstractShock tube pyrolysis of propane at temperatures between 1300 K and 2700 K at reflected shock pressures of 500 to 1500 kN/m2 has been investigated. The reaction is of 1st order with a rate constant K = 1.79 × 108 exp (‐176.2 kJ/RT) s−1. The major reaction products were acetylene, ethylene and methane, while traces of propylene and ethane were only detected at temperatures below 1500 K. At higher temperatures, propane conversion to acetylene increased at the expense of the other products. Optimum conversions to ethylene and methane, in contrast to that to acetylene, were more sensitive to changes in temperature than to variations in reaction time. However, at reaction pressures above 550 kN/m2, extension of reaction time beyond 0.5 ms did not favour the formation of acetylene. A simple kinetic model which confirmed the experimental optimum product selectivity conditions is put forward.
Mass transfer and reaction behaviour of a circulating fluidized bed reactor
Authors: Vollert Joachim , Werther Joachim 
Published: August 2005

AbstractThis contribution presents a chemical reactor model of a circulating fluidized bed (CFB) which takes into account adsorption effects and provides a description of the vertical profiles of gas concentration in the riser. The oxidation of NO is used as an example of a heterogeneous catalytic reaction. Mass transfer between the gas phase and solid particles in the CFB was investigated at various temperatures and solids mass flow rates. The measurements show that the mass transfer coefficient decreases with increasing solids mass flux and that the CFB resembles a bubbling fluidized bed as regards gas‐solid contacting.
Optimal experimental procedures in a combined TPR/TPO apparatus
Authors: Jouguet Bernadette , Gervasini Antonella , Auroux Aline 
Published: August 2005

AbstractThe apparatus described allows successive TPR/TPO experiments on the same sample. A calibration method for the reducing or oxidizing gas mixture is described. The best operating conditions for optimal results and sensitivity are discussed. We have studied the application of TPR/TPO to bulk V2O5 and to the redox behaviour of CuII ions on silica‐alumina. The procedure resulted in reproducible TPR/TPO profiles.
Rotational particle separator: A new method for separating fine particles and mists from gases
Authors: Brouwers Bert 
Published: August 2005

AbstractAn account is given of the patented technique of the rotational particle separator for separating solid and liquid particles of diameter 0.1 μm and larger from gases. Attention is focused on the working principle, fluid mechanical constraints, particle design, separation performance, power consumption, dimensions, filter cleaning and costs. Furthermore, an overview is given of current developments to introduce this technique in industrial dust removal, in electricity generation and in the consumer goods market. The article concludes with a summary of the feature which distinguish this technique from existing filtering methods.
Sulzer BX gauze: Fluid dynamics and absorption of acid gases
Authors: Nardini Giuliano , Paglianti Alessandro , Petarca Luigi , Viviani Elena 
Published: August 2005

AbstractThe aim of this work is a fluid dynamics study of the structured packing Sulzer BX gauze. A new model is proposed which, on the basis of a knowledge of the dynamic component of the liquid holdup, permits calculation of the fraction of the geometric area of the packing that effectively participates in the mass transfer. Both the metal and plastic versions of the packing are studied. Experimental data are supplied on the absorption of pollutants such as HCl and SO2 by aqueous solutions of NaOH in columns in cocurrent operation. The results obtained by the proposed model are in good agreement with experimental data obtained by the present authors as well as with experimental data published in the literature.
A review of some parameters involved in fluidized bed bioreactors
Authors: Wright Phillip C. , Raper Judy A. 
Published: August 2005

AbstractThree‐Phase fluidized bed bioreactors have advantages over conventional chemical reaction systems. There is a lack of agreement over most major operational conditions, and a wide range of design variables are open to question. A large body of recent work in the field has been reviewed, with a degree of historical comparison and discussion.It has been found that aspects of fluidized bed biofilm reactors of vital importance include: choice of solid media, gas and liquid loadings, bacterial type and reactor mechanical design. A large proportion of the work in the field of three‐phase fluidization is non‐biologically specific, or not tested on a bacterially inoculated system.The majority of three‐phase fluidized bed bioreactor work is in the field of water treatment. Although this work has highlighted the potential for use of bio‐fluidized beds for this application, there are still specific problems hindering the large scale industrial acceptance of three‐phase fluidized bed bioreactors.
An investigation of the phase transformations in a CaSO4/(NH4)2SO4/H2O system, directed at the preparation of a fine dispersed purified phosphogypsum
Authors: Bojinova Darinka , Gruncharov I. 
Published: August 2005

AbstractThe process of recrystallization of apatite phosphogypsum (PHG) in a solution ammonium sulphate (AS) with the subsequent decomposition of the binary salt was investigated and the resulting highly dispersed products with a low P2O5 content have been discussed. The following effects were examined: (NH4)2SO4 concentration, the quantity of ammonium sulphate, the reaction temperature of phosphogypsum with (NH4)2SO4 solution, the time of treatment of phosphogypsum with (NH4)2SO4 solution and the decomposition of the binary salt, as well as the liquid/solid ratio for the binary salts, Based on the results of the chemical and X‐ray analysis, it was established that, depending on the technological conditions of the process of recrystallization, binary salts of (NH4)2SO4·CaSO4·H2O and of (NH4)2SO4·CaSO4·H2O and of (NH4)2SO4·5 CaSO4·H2O were formed. As a result of the investigations carried out, a product with a low P2O5 content, suitable for direct processing to secondary products has been prepared.
Behavior of three‐way catalyst in a hybrid drive system
Authors: Padeste Lukas , Tagliaferri Sergio , Baiker Alfons 
Published: August 2005

AbstractThe dynamic behavior of a Pt‐Rh/CeO2‐Al2O3 three‐way catalyst (TWC) under pulsed flow operation conditions (intermittent mode), such as occur in a newly developed hybrid drive system, has been studied experimentally in a laboratory apparatus with simulated exhaust gas. The parallel hybrid system is based on the combination of an Otto‐cycle engine with an electric motor and a flywheel providing a short‐term energy storage. This configuration permits intermittent charging of the flywheel by the combustion engine which runs only during about 10% of the driving time. Each exhaust gas pulse (duration typically ca. 3 s) is proceeded by an air pulse, which results from the filling of the engine cylinders with air at start up and shut off. Experimental studies indicated that the air pulses have a negative impact on the performance of the catalytic converter, reducing the inherent benefits resulting from the intermittent operation mode of the combustion engine.Forced asymmetric λ‐cycling during exhaust pulse was found to be most beneficial for improving catalyst performance. A simple reduced kinetic model derived from a Langmuir‐Hinshelwood model for CO oxidation, which was extended by introducing CO and O2 equivalents to mimic the complex exhaust gas, was used to describe the dynamic behavior of the TWC. The model proved to be useful for finding the optimal λ‐cycling conditions. Experiments with the real Otto‐cycle engine exhaust proved that the reduced kinetic model is suitable for use in a closed loop λ‐control.