bluuebunny/crossref_metadata_2025 huggingface dataset:
Heel contact as a function of substrate type and speed in primates
Authors: Schmitt Daniel , Larson Susan G.
Published: August 2005

In this report we provide detailed data on the patterns and frequency of heel contact with terrestrial and arboreal supports in primates. These data can help resolve the question of whether African apes and humans are uniquely “plantigrade” (Gebo [1992] Am. J. Phys. Anthropol. 89:29–58; Gebo [1993a] Am. J. Phys. Anthropol. 97:382–385; Gebo [1993b] Postcranial Adaptation in Nonhuman Primates), or if plantigrady is common in other primates (Meldrum [1993] Am. J. Phys. Anthropol. 91:379–381). Using biplanar and uniplanar videotapes, we recorded the frequency and timing of heel contact for a variety of primates (32 species) walking on the ground and on simulated arboreal supports at a range of natural speeds. Our results indicate that Pongo as well as the African apes exhibit a “heel‐strike” at the end of swing phase. Ateles and Hylobates make heel contact on all supports shortly after mid‐foot contact, although spider monkeys do so only at slow or moderate speeds. Data available from uniplanar videotapes suggest that this pattern occurs in Alouatta and Lagothrix as well. No other New or Old World monkey or prosimian in this study made heel contact during quadrupedalism on any substrate. Thus, heel contact occurs in all apes and atelines, but only the great apes exhibit a heel‐strike. We suggest that heel contact with the substrate is a by‐product of an active posterior weight‐shift mechanism involving highly protracted hindlimbs at touchdown. Force plate studies indicate that this mechanism is most extreme in arboreally adapted primate quadrupeds walking on arboreal supports. Although heel contact and heel‐strike may have no evolutionary link, it is possible that both patterns are the result of a similar weight shift mechanism. Therefore, the regular occurrence of heel contact in a variety of arboreal primates, and the absence of a true biomechanical link between limb elongation, heel contact, and terrestriality, calls into question the claim that hominid foot posture was necessarily derived from a quadrupedal terrestrial ancestor. © 1995 Wiley‐Liss, Inc.
Mitochondrial DNA of the Mauritian macaques (Macaca fascicularis): An example of the founder effect
Authors: Lawler Susan H. , Sussman Robert W. , Taylor Linda L.
Published: August 2005

Macaque monkeys (Macaca fascicularis) were introduced to the island of Mauritius approximately 400 years ago. This study compares the mitochondrial DNA of macaques on Mauritius with those from Indonesia and the Philippines. The goal is to measure the amount of evolutionary change that has occurred in this isolated population over 400 years, and to address questions regarding the origin of the Mauritian founders. Amplification of the control region of the mitochondrial genome via the polymerase chain reaction yielded an 1800 base pair DNA fragment which was surveyed for variation using restriction endonucleases. Fifty‐two macaques were separated into 17 haplotypes by mapping the restriction sites. No haplotypes were shared among the three populations, and only two closely related haplotypes appeared in the Mauritian sample. Nucleotide variation in the mitochondrial DNA in the Mauritian sample was 10‐fold less than the Indonesian and Filipino samples. In contrast, allozyme data estimates of genetic diversity on Mauritius are similar to populations from the ancestral range. The evidence of the more severe bottleneck as measured by mitochondrial data may be explained in part by almost exclusive male dispersal in this species, and may support models of founder events in which rapid population growth prevents substantial loss of nuclear variation. The mitochondrial evidence supports the morphologically and historically based hypothesis that the original founders came from Indonesia. © 1995 Wiley‐Liss, Inc.
HLA‐DRB1 frequencies of non‐Austronesian‐speaking Gidra in south New Guinea and their genetic affinities with Oceanian populations
Authors: Yoshida Maki , Ohtsuka Ryutaro , Nakazawa Minato , Juji Takeo , Tokunaga Katsushi
Published: August 2005

DNA typing of HLA‐DRB1 genes was conducted for 192 samples from the Gidra who speak one of the non‐Austronesian languages and inhabit the southern lowlands of New Guinea. Comparison of the allele frequencies with those of eight other Oceanian populations reveals that the Gidra are genetically closest to the non‐Austronesian‐speaking Goroka and, next, to the Aboriginal Australian groups, but are remote from the Austronesian‐speaking groups in mainland New Guinea and the rest of Melanesia. This finding clearly supports the hypothesis that non‐Austronesians and Aboriginal Australians are descendants of the first‐stage migrants to Oceania. © 1995 Wiley‐Liss, Inc.
Ohalo II H2: A 19,000‐year‐old skeleton from a water‐logged site at the Sea of Galilee, Israel
Authors: Hershkovitz I. , Speirs M. S. , Frayer D. , Nadel D. , Wish‐Baratz S. , Arensburg B.
Published: August 2005

The discovery of well‐preserved human remains at the site of Ohalo II in the northern Jordan Valley substantially augments the meager fossil record of the Levantine late Upper Pleistocene. The Ohalo II H2 specimen, dated to ca. 19,000 B.P., is the most complete early Epipaleolithic hominid discovered in Israel and promises to contribute to the clarification of a number of problematic issues in the local evolution of anatomically modern humans. In addition to a description of the burial and its Kebaran context, a detailed anatomical description of the skeleton is offered and morphometric comparisons are made to other Upper Paleolithic hominids. Ohalo II H2 is shown to demonstrate affinities in the craniofacial skeleton to fossils from the early Upper Paleolithic and late Epi‐Paleolithic of the Levant. © 1995 Wiley‐Liss, Inc.
Sexual dimorphism in the snub‐nosed langurs (Colobinae: Rhinopithecus)
Authors: Jablonski Nina G. , Ruliang Pan
Published: August 2005

Sexual dimorphism in the dentition and skeleton of the four extant species of snub‐nosed langurs, Rhinopithecus (R.) bieti, R. (R.) brelichi, R. (R.) roxellana and R. (Presbytiscus) avunculus, was studied. The species shared a similar general pattern of sexual dimorphism, but were found to differ in respects that appear to reflect the influence of disparate socioecological and environmental factors. All the species showed marked canine dimorphism, but the very high degree of canine dimorphism in R. bieti appeared to be due to the intensity of intermale competition for mates during a temporally restricted breeding season, and possibly also to the intensity of competition between males for other resources during other times of the year. Sexual dimorphism in the postcranial skeleton of Rhinopithecus species was also most pronounced in R. bieti and may be related to the relatively higher frequency of terrestrial locomotion in males of the species. © 1995 Wiley‐Liss, Inc.
Pattern profile analysis of hominid and chimpanzee hand bones
Authors: Smith Shelley L.
Published: August 2005

In a study designed to complement morphological research on hominid hand bones, length and width measurements of the thumb, index, and middle rays were obtained from radiographs of modern human hands. These rays are primary in precision‐gripping postures and are therefore the ones most relevant for investigating evolutionary changes in fine manipulation. Pattern profile analysis allows individuals or samples to be plotted against a reference sample in standard deviation units, or Z‐scores. It provides an indication of how different measurements are from modern human averages, while taking into consideration the degree of variation present within modern human samples. A pattern profile for chimpanzees is clearly distinct from humans but quite similar to that of a bonobo, demonstrating the promise of pattern analysis. Partial pattern profiles of several of the more complete early hominid bones from Hadar, Swartkrans, and Olduvai (O.H. 7) are presented and compared. Hadar bones are long and wide at midshaft relative to articular widths; both body‐size effects and functional differences are likely. Thumb distal phalanges from Swartkrans and Olduvai both have relatively small base widths, but they differ in other proportions. Two first metacarpals from Swartkrans show distinct patterns. The profiles of La Ferrassie I and Shanidar IV show the characteristically large Neanderthal distal phalanges. Profiles of Skhūl IV and Předmost III are alike in some regions with reference to modern North American white males, though they are less similar overall than are those of the two Neanderthals. © 1995 Wiley‐Liss, Inc.
Use of carbon dioxide in industrial organic syntheses
Authors: Behr Arno
Published: August 2005

Although carbon dixoide is important as an abundant carbonaceous raw material, so far, its utilization in chemical processes has been rather limited. This review covers the reactions of CO2 employed in industry, such as the production of urea, the Kolbe‐Schmitt reaction, the synthesis of cyclic organic carbonates and the use of CO2 in methanol synthesis. Interesting recent developments in CO2 chemistry, such as the reactions catalyzed by transition metals, are also described. Apart from the synthesis of polymers and hydrocarbons, the production of oxygen‐containing substances appears to be very profitable and attractive for future industrial applications. Not only can derivatives of formic and carbonic acids be produced but also longer‐chain carboxylic acids and their derivatives by reactions of carbon dioxide with hydrocarbons such as alkynes, alkenes and 1,3‐dienes.
A new method for measuring local velocities of the continuous liquid phase in strongly aerated gas‐liquid multiphase reactors
Authors: Lübbert Andreas , Larson Bernd
Published: August 2005

A new measurement method for determining the local liquid‐phase velocities in multiphase flows is presented. It is based on a tracer technique, using heat introduced into the flow, seemingly at random, instead of a material tracer. The input of heat pulses and measurement of temperature at an adjacent point is performed by small probes. As an intermediate result, the flow time distribution of the heat‐labelled fluid elements is calculated on‐line as a cross‐correlation function between the pseudo‐random input and the measured output signals. This calculation and the automatic control of measurements is carried out by a simple microprocessor unit. The device produced excellent results in gas‐liquid flows at high gas throughputs and high liquid‐phase velocities.
Kinetics of removal of impurities from gases by high pressure adsorption
Authors: Groninger Günter , Hedden Kurt , Ramananda Rao B.
Published: August 2005

Among other processes, adsorption is used for the removal of hydrogen sulphide from natural gases. Hereby, competitive adsorption of the different gas components plays an important role, e.g., that of carbon dioxide. Data of equilibrium loading and adsorption kinetics are required for the design of adsorbers, filled with molecular sieve. In order to obtain these data under the prevailing operating conditions, hydrogen sulphide was removed from gas mixtures H2S/CH4 and H2S/CO2/CH4, in a pilot plant, by adsorption on molecular sieve 5A. The equilibrium loading, the height of transfer zone, and the length of unused bed were determined from the measured breakthrough curves of H2S. With these data, the breakthrough time and the optimum process conditions were calculated for a practical example.
Continuous deasphalting of heavy petroleum residues with ethyl acetate
Authors: Höucker Jürgen , Vogelpohl Alfons
Published: August 2005

When crude oil is vacuum distilled, about 30% of the feed remain as low value residue. Hydrocracking can upgrade this residue into valuable light hydrocarbons. The hydrocracking could be optimized catalytically, if the residue were not to contain the metals vanadium and nickel that poison the catalyst. This contribution shows that continuous extraction of the residue with ethyl acetate yields a fraction with low metal content, while an asphaltene fraction with the remaining metal content is filtered off.
Simulation of fluid dynamics in a pulsed sieve plate column
Authors: Haverland Hartmut , Vogelpohl Alfons , Gourdon Christophe , Casamatta Gilbert
Published: August 2005

The present contribution reports on a new method for the simulation of the dispersed phase behaviour in liquid‐liquid extraction columns. The fluid dynamic description is based on a mathematical model which explicitly takes into account drop transport, break‐up and coalescence mechanisms, via a drop population balance along the column. Application of the model requires some simple measurements on single drops in order to determine transport and break‐up laws, which are required by the model, and possibly also coalescence parameters. In this study the model is applied to pulsed sieve plate columns. The specific example considered here is based on systematic studies on the determination of break‐up rates from the corresponding probabilities of break‐up and the generated daughter drop size distributions by means of high‐speed photography. The validity of the model was subsequently tested by comparison with some experimental results from studies on two different pulsed columns 80 and 225 mm in diameter for the water/toluene system without mass transfer. The satisfactory agreement between the results justifies the use of such a method for the description of the behaviour of liquid‐liquid extraction columns in a wide range of operating conditions. Furthermore, application of the model may help to dispense with long and expensive pilot tests.
DIVA – a flow‐sheet oriented dynamic process simulator
Authors: Marquardt Wolfgang , Holl Peter , Gilles Ernst Dieter , Butz Dieter
Published: August 2005

The detailed dynamic simulation of coupled process units in chemical plants is gaining an increasing importance as a useful tool in plant engineering and operation. The outline of the program package DIVA (Dynamische Simulation verfahrenstechnischer Anlagen) which is currently under development is presented in the following. The dynamic plant equations and the corresponding Jacobian matrix are generated automatically. The full exploitation of sparse matrix techniques in combination with stiff ODE (ordinary differential equation) solvers allows an efficient solution of all the equations simultaneously. The possibilities offered by the simulator are demonstrated by the simulation of two laboratory plants.
Contact‐free measurements of oxygen concentration in industrial flames by raman scattering
Authors: Leipertz Alfred , Haumann Jürgen , Fiebig Martin
Published: August 2005

Spatially resolved oxygen concentration measurements were performed in premixed hydrocarbon flames by using laser induced spontaneous Raman scattering. The measurements demonstrate the performance of a relatively simple pulsed laser Raman probe for fundamental combustion studies and also for the control of the equivalence ratio in flames (best spatial resolution: 0.2 mm3; theoretical detection limit: 0.8% of O2). Comparison of the results with those obtained by a mechanical suction probe (Magnos 2 T) confirmed a good agreement. At present, control of different stoichiometric conditions is possible at a minimum O2 concentration of 1.3%.
Oxygen and methane enrichment — a comprison of module arrangements in gas permeation
Authors: Rautenbach Robert , Dahm Wolfgang
Published: August 2005

In the separation of gaseous mixtures by gas permeation, it is in some cases impossible to achieve the desired product quality in a single stage and, therefore, several stages may be necessary. Multistage processes can be implemented by membrane modules arranged in the form of a cascade or by a membrane column design. On the basis of an economic analysis, this paper discusses different possible module arrangements for 2 cases, i.e. the enrichment of oxygen from air and the separation of methane from biogas. Present calculations indicate that, in the first case, two‐stage cascades with or without recycle and, in the second case, one‐stage cascade without recycle constitute the optimum module arrangements. However, depending on the selling price of the methane enriched gas, one‐ or two‐stage cascades with recycle have to be considered. Finally, It was shown that, in the permeation of non‐ideal gases, the Joule‐Thomson effect has to be taken into account.
Flow‐induced vibrations of tube arrays in cross‐flow
Authors: Troidl Hubert , Strohmeier Klaus
Published: August 2005

Existing heat exchanger design criteria do not satisfy the continually increasing requirements for greater efficiency or mass flux and energy throughput. Occasionally, failures appear even after only a few hours of operation, as shown in section 3. A long series of experiments, often carried out on original scale, did lead to the derivation of a large number of empirical expressions; however, physical explanations of the complex tube‐failure interactions could not as yet be found. In contrast, experiments with a well defined simple model, whereby the tube deflections were recorded digitally and, at the same time, tube‐fluid interactions were registered on a high‐speed film, show that elementary “fluid transport mechanisms” control the stability behaviour of the heat exchanger tubes. Vibration excitation mechanisms such as “galloping”, “jet switching” and “whirling” (fluid elastic coupling) proved, with their characteristics, as typical for the vibration behaviour of single rows within the tube array, but not for the vibration phenomena of tube bundles.
Conversion of organic oxygen compounds and their mixtures on H‐ZSM‐5
Authors: Fuhse Jürgen , Bandermann Friedhelm
Published: August 2005

The conversion of a number of alcohols, ethers, ketones, aldehydes, carboxylic acids, esters, and cyclic compounds and their mixtures on H‐ZSM‐5 at 673 K was investigated. These compounds can be easily converted to aromatic hydrocarbons if the C/H ratio of the molecule fragment, remaining after elimination of oxygen as water, is less than 0.62. At higher C/H ratios, coking of the catalyst increases, thus reducing its lifetime, a difficulty which can be overcome by hydrogenation of these compounds prior to their conversion over H‐ZSM‐5. A procedure is proposed for converting at least a part of organic waste chemicals to valuable products instead of burning them.
Comparison of performance of an industrial VGO‐treater with reactor model predictions
Authors: Döhler Werner , Rupp Martin
Published: August 2005

A simplified reactor model can be used for predicting the performance of an industrial VGO‐treater. Laboratory‐scale experiments performed on the same feed and catalyst as those in the industrial unit lead to a reactor simulation which agrees well with the data from this unit. In the laboratory experiments, it is possible to overcome the specific hydrodynamic problems of tricklebed reactors by appllying the catalyst dilution technique. Results obtained by this technique allowed the development of a reactor model which enables the user to simulate the adiabatic behaviour of the industrial reactor. In this way, the significant gap between the reaction temperature in the isothermal laboratory reactor and the WABT of the industrial adiabatic reactor can be bridged.
Kinetic studies on catalytic methanation by means of a concentration‐controlled recycle reactor
Authors: Löwe Arno , Tanger Uwe
Published: August 2005

The rate behaviour of multi‐step reaction systems is difficult to model. Concentration‐controlled investigations in a recycle reactor provide new tools for this purpose, e.g. the possibility to decompose a network into single reaction steps. Methanation of carbon monoxide over a supported Ni catalyst could be shown to be accompanied to a considerable extent by the shift reaction, and to a lesser extent by direct hydrogenation of carbon dioxide. Deactivation of the catalyst was measured at definite gas compositions. The two main steps show different responses to deactivation: Separable kinetics was found only for the methanation step. Power law rate equations were fitted to the rate data of the individual reaction steps to represent the main features of their kinetic behaviour. Some aspects of deactivation kinetics are also discussed.
A differential model for a countercurrent extractor column with non‐constant flow rates, interfacial area per unit volume and axial dispersion coefficients
Authors: Cornelissen A. E. , Grievink J. , Toneman L. H.
Published: August 2005

In the extraction literature, no attention has been given so far to differential calculation models for countercurrent extraction columns which take into account the changes in flow rates of the phases as a result of transferred mass, and which also reflect the variations in interfacial area per unit volume and in axial dispersion coefficients since these depend on the flow rates. The present contribution puts forward a formulation of such a model; this results in a set of non‐linear differential equations with separated boundary conditions, representing the feeds at either side of the extraction column. This set of differential equations must be solved numerically. The model is illustrated by a sample calculation on the extraction of benzene with furfural. In this (realistic) example, the interfacial area per unit volume varies from bottom to top by a factor of 3. Ignoring this effect would obviously result in serious under‐ or overdesign.
A model for the rate of catalytic oxidation of methanol in a fixed bed reactor
Authors: Sohrabi Morteza , Dabir Bahram , Mozaffari Farhad
Published: August 2005

Oxidation of methanol to formaldehyde, using a mixture of ferric and molybdenum oxides as catalyst, has been studied in a fixed bed integral reactor, 150 mm long, 25 mm o.d. and 10 mm i.d. The catalyst was prepared by reaction between aqueous solutions of ammonium heptamolybdate and ferric chloride. It has been shown that, under experimental conditions similar to those employed in industry, neither external nor internal diffusion had been effective in the process and isothermal conditions prevailed in both gas and solid phases. A two‐step mechanism has been put forward for the oxidation of methanol. According to such a mechanism, methanol is first oxidized to formaldehyde, accepting an oxygen molecule from the catalyst and changing the latter into a reduced form. In the second step, the reduced catalyst is transformed into the original form on obtaining an oxygen molecule from the gas phase. Based on this scheme, a rate model has been derived and verified by experimental results.
An improved method for flow network design
Authors: Lin Sheng H.
Published: August 2005

An improved method is presented for the design of a complex flow network system. The method employs head loss and flow rate in the iteration process for the determination of flow rates and/or pressure drop. This represents a major departure from the conventional approach which uses only the flow rate. The two‐step iteration method proposed here drastically improves both the convergence rate and iteration stability. Tests on different examples have shown that, for most design applications, three iterations are sufficient to yield an accurate final solution, regardless of the initial guess.
Application of dynamic programming to high‐dimensional systems described by difference equations
Authors: Luus Rein , Smith Stephanie G.
Published: August 2005

The application of dynamic programming using an interative procedure, which employs domain contraction and accessible grid points for the state vector, is investigated for solving optimal control problems where the system is described by a set of difference equations. A model of a gas absorber with six state variables and two control variables is used to examine the feasibility of the proposed algorithm and to analyze the effects of the grid size and of the domain contraction factor. This algorithm yields rapid convergence to the optimum even when a relatively coarse grid with as few as 11 grid points is used.
A new process for indirect gas supply by means of perfluorinated polyethers
Authors: Schäfer Hans , Bayer Thomas , Buchholz Rainer , Kühlein Klaus , Schlingmann Merten , Wullbrandt Dieter
Published: August 2005

A new process has been developed for indirect gas supply for culturing shear sensitive cells by means of a perfluorinated hydrocarbon. Hostinert 216, a perfluorinated polyether, was used as oxygen and carbon dioxide carrier. Hydrodynamics and mass transfer, required for industrial implementation, were investigated in a drop column. Based on the knowledge, obtained with indirect gas supply, it has been possible to construct a waste‐gas free sterile pilot plant. Correlations derived from performed measurements permit design of and scale‐up to an industrial plant.
Studies of drop break‐up in liquid‐liquid systems in a rotating disc contactor. Part II: Effects of mass transfer and scale‐up
Authors: Bahmanyar Hossein , Dean D. Roy , Dowling Irena C. , Ramlochan Kenrick M. , Slater Michael J. , Yu Wei
Published: August 2005

The number fraction of drops of a given size which break up at rotor level in a rotating disc contactor has been observed during mass transfer in either direction to or from solvent or aqueous drops. Critical rotor speeds for a given drop size undergoing mass transfer can be used to find an effective interfacial tension. Using this interfacial tension value, the break‐up fractions are correlated within experimental uncertainties in the same manner as for no mass transfer. Drop break‐up fractions depend on column size and relevant empirical correlations of the data are presented. The results may be used to estimate the effect of mass transfer on drop size distributions in an RDC.
Three‐component mass transfer in liquid‐liquid extraction with the system glycerol‐acetone‐water. Part 1: The influence of vanishing diffusion coefficients in binodal states on the mechanisms of mass transfer
Authors: Schermuly Wolfgang , Blass Eckhart
Published: August 2005

This contribution deals with the consequences of the decrease in diffusion coefficients at the boundaries of miscibility in fluid systems and its effect on the mechanisms of mass transfer. The liquid‐liquid (1–1) extraction involving several components is taken as an example for the discussion of this topic. A short review of Hampe's theory on transport mechanisms in the transition regions of interfaces [1] explains the intrinsic interdependence between mass and momentum transfer. Finally, a discussion of the peculiarities of resistances to mass transfer in boundary layers, based on the changes in molecular transport properties, is presented.
Influence of intraparticle total pressure change on pore mass transport
Authors: Scholl Stephan , Mersmann Alfons
Published: August 2005

Influence of intraparticle total pressure change on pore mass transport is investigated in physical gas phase adsorption of a single component from an inert carrier medium. The Dusty Gas Model is applied to quantify pore mass transport, assuming local equilibrium between pore fluid and adsorbed phase. Calculated results for single pellet adsorption kinetics of cyclohexane on activated carbon and CO2 on molecular sieve 5 Å are compared with experimental data. It is found that the total pressure drop in the pore system may be as much as 1% of the ambient total pressure. This results in a maximum viscous flow contribution of 13% for the cases studied. Since this contribution is obtained only under conditions of low overall transport rates of the adsorbed component, the assumption of isobaric conditions within the pore system of a porous adsorbent appears justified for most cases of practical calculations.
Role of sparger design in mechanically agitated gas‐liquid reactors. Part II: Liquid phase mixing
Authors: Rewatkar Vilas B. , Joshi Jyeshtharaj B.
Published: August 2005

Liquid phase mixing time was measured in 0.57, 1.0 and 1.5 m i.d. mechanically agitated gas‐liquid reactors. Transient conductivity technique was used for the mixing time measurement. Pitched blade downflow turbine was employed. The design details of PTD impellers such as diameter (0.22 T to 0.5 T) and blade width (0.25 D to 0.35 D) were studied. The influence of sparger types and their design on mixing time has been investigated. For this purpose, pipe, ring, conical, and concentric ring spargers were employed. The design details of the ring sparger, i.e. ring diameter, number of holes and hole size were also studied in depth. Sparger location with respect to the impeller was found to be the most important variable and, therefore, it was varied for practically all the spargers studied in this work. It was found that the liquid phase mixing time depends on the impeller design, sparger design, sparger location, impeller speed and superficial gas velocity. Correlations have been developed for the dimensionless mixing time.
Equilibrium model for CO2 absorption in an aqueous solution of 2‐amino‐2‐methyl‐1‐propanol
Authors: Erga G. Olav , Lidal Håvard
Published: August 2005

A semi‐empirical gas‐liquid equilibrium model for the absorption of CO2 in aqueous 3M AMP (2‐amino‐2‐methyl‐1‐propanol) is presented. It applies to high CO2 loadings (y > 0.5) in the temperature range between 20 and 50 °C, and is based on experimental solubility and pH determinations. For a given amine concentration, it yields the equilibrium partial pressure of CO2 as a function of only two variables: the CO2 loading and temperature. The model correlates the expressions for the chemical equilibria involved as follows: p = m y × 10x, where p is the equilibrium partial pressure, x = logK ‐ pH, m is the amine molarity, y the CO2 loading, and K is a parameter involving Henry's law constant, H, and the first dissociation constant, K1, of carbonic acid. pH is found to depend on both temperature and CO2 loading while logK depends only on the CO2 loadIng. Correlations for pH and logK are presented. The model fits own data for 3M AMP very well as well as the equilibrium data found in recent literature.
Hydrodynamics in a pressurized cocurrent gas‐liquid trickle‐bed reactor
Authors: Wammes Wino J. A. , Westerterp K. Roel
Published: August 2005

The influence of gas density on total external liquid hold‐up, pressure drop and gas‐liquid interfacial area, under trickle‐flow conditions, and the transition to pulse flow have been investigated with nitrogen or helium as the gas phase up to 7.5 MPa. It is concluded that the hydrodynamics depends on the gas density and not on the reactor pressure. At higher gas densities, the operating region for trickle flow becomes larger while the gas‐liquid interfacial area increases only slightly. Pressure gradient and liquid hold‐up are considerably affected by gas density and correlations have been derived for these parameters.
Effect of thermal pretreatment and reduction on acidity and metal state in doped NiH and CuH mordenites
Authors: Exner Herbert , Fetting Fritz
Published: August 2005

Thermal pretreatment such as calcination and steaming as well as the reduction of cations by hydrogen, affect the zeolitic acidity and activity of nickel‐ and copper‐doped mordenites in heterogeneously catalyzed reactions such as the conversion of n‐hexane. Data on acidity changes were obtained by IR spectroscopy, and information on ionic and metallic states by temperature‐programmed reduction, CO chemisorption and transmission electron microscopy (TEM). The findings were compared with reaction results from conversion of n‐hexane. Trimethylamine (TMA) was selected as a standardization molecule for semi‐quantitative determination of acidity. Correlation of relative acidity values with experimental results was possible only to a very limited extent. Results of CO chemisorption, TPR and TEM allow conclusions to be drawn on metallic crystallites, Ni+ and Cu+ ions and clusters, which appear to exert a stabilizing influence on zeolitic activity. Nickel crystallites with d > 2 nm catalyze both hydrogenation and dehydrogenation of paraffins on the metal in bifunctional catalysis, as was also observed on platinum‐doped zeolites.
Heat, mass and momentum transfer in packed bed distillation columns
Authors: Karlström Anders , Breitholtz Claes , Molander Mats
Published: August 2005

This contribution presents the basic equations for heat, mass and momentum transfer in multicomponent packed bed distillation processes. In some situations, the use of strongly simplified models is justified, but when approaching more difficult and, at the same time, economically more interesting regions of operation where non‐linear effects are significant, these models are likely to fail. Consequently, a more rigorous vapour‐liquid equilibrium model should be employed since the pressure drop in the column will not be negligible in those regions. Furthermore, neither constant parameter hold‐ups nor heat and mass transfer coefficients are assumed. Simulations demonstrate some interesting process properties. The impact of the surroundings on the process is discussed and a three‐dimensional model extension is outlined.
On the permeability of binary packings of spheres
Authors: Andrade José S. , Rajagopal Krishnaswamy , Benyahia Farid , Foumeny Esmail A. , McGreavy Colin
Published: August 2005

Macroscopic flow properties of packed beds are strongly dependent on the structure of the pore space. In the case of permeability, the classical approach in which this coefficient is related to the mean voidage cannot be systematically applied as a predictive methodology, because the mean voidage index does not account for the morphology and topology of the porous media. In this work, a modelling technique is developed which enables the effective permeability of a binary packing of spheres to be evaluated from a detailed structural and phenomenological description of the system. The results are then compared with experimental data to confirm the predictive capability of the model.
Investigations on increasing safe gas volumetric flow rate through a water trap flame arrester
Authors: Rubach Torsten , Schecker Hans‐Georg , Jäger Walter Rudolf , Onken Ulfert
Published: August 2005

In the process industries, safety problems may arise when combustible gases are transported through pipes. Therefore, it is necessary to prevent propagation of flame fronts into or through systems, in order to avoid undesired explosions and flashbacks into the production plant. Safety devices which are used in such cases are the flame arresters, e.g. water trap flame arresters. There is a maximum gas flow rate through a water trap flame arrester below which a flashback is unlikely to occur. Based on investigations of the explosion behaviour of bubbles in suspensions of glass spheres, experiments were carried out in a water trap flame arrester of industrial demensions. It is shown that the safe gas volumetric flow rate through a water trap flame arrester can be increased by up to 30% for H2/air mixtures when glass spheres are added to the liquid in the flame arrester.
A multiple state stochastic model for deep‐bed filtration
Authors: Tarafdar Suparna , Dey Avijit , Gupta Bhaskar Sen
Published: August 2005

A one‐parameter stochastic model has been developed for the prediction of dynamic pressure drop in a deep‐bed filter. The model is based on a finite‐state and discrete‐time Markov chain method whereby the pressure drop in a deep‐bed filter can be estimated at discrete time intervals. The proposed model is simpler than the stochastic birth and death models available in literature. The bed is assumed to pass through different states of porosity during the filtration and it is spatially lumped in each state. For pressure drop calculation, the Carman‐Kozeny equation is used in conjunction with the Payatakes‐Tien‐Turian model. Model equations are simple and can be easily solved on a personal computer. The theoretical results agree well with the plant data as well as with the available experimental data.
Heat transfer mechanisms in gas fluidized beds. Part 3: Heat transfer in circulating fluidized beds
Authors: Molerus Otto , Mattmann Wolfgang
Published: August 2005

Part 1 of this contribution reported on the effects of system properties on heat transfer between heating or cooling surfaces and bubbling fluidized beds. This investigation produced four correlations which define the respective maximum heat transfer. Part 2 of this study suggests that the heat transfer between exchanger surfaces and bubbling fluidized beds depends on superficial gas velocity, expressed as dimensionless excess gas velocity. The present paper shows that heat transfer coefficients in circulating fluidized beds can be predicted by evaluation of a state diagram, which combines three dimensionless groups: Nusselt number, Archimedes number and a dimensionless pressure gradient. A comparison of coal combustion experiments with own cold model measurements indicates that the radiative component of heat transfer coefficients is only evident at very low dimensionless pressure gradients.
Fatigue of thick‐walled pipes from soft martensitic and semi‐austenitic chrome‐nickel steels under pulsating internal pressure
Authors: Vetter Gerhard , Lambrecht Diethelm , Mischorr Gerhard
Published: August 2005

Thick‐walled components subjected to pulsating internal pressure are widely applied in high‐pressure technology and in manufacturing processes such as fluid‐jet cutting and high‐pressure cleaning, mainly in conjunction with reciprocating pumps. Corrosive fluids require high‐strength and tough chrome‐nickel steels with soft martensitic or semi‐austenitic structure. This contribution reports on the fatigue of thick‐walled plain and cross‐bored pipes made from high alloy chrome‐nickel steels such as X5 CrNiMoCu 21 8 and X5 CrNiMo 16 5. The speciments, uniaxial standard form and thick‐walled pipes, were cut from forged blocks in the three axial directions. For loading with pulsating pressure, a suitable, high‐frequency piston pulsation machine has been developed. The fatigue tests on pipe specimens show typical Woehler characteristics with only slight scatter and relatively good isotropy. The surprisingly large admissible pulsating pressure can be explained for the applied steels by dynamic generation of residual stresses as a result of shake‐down effects. Presentation in a Smith digram explains the occuring dynamic shake‐down and its favourable results in comparison to the more brittle highly tensile steels. It also reveals that heat treatment to higher tensile strength does not always yield an increase in the admissible pulsating pressure. It will be shown that static autofretting and shake‐down affect the fatigue strength of thick‐walled pipe specimens in the same way. Tests with internal liners in the tube specimens provide indications on the sensitivity of material failures towards fluids. The investigation aids the understanding of the fatigue behaviour and the design of components made of modern high‐strength corrosion resistant steels.
Physical properties of the NO‐absorbing system nitric acid‐tributyl phosphate
Authors: Pham Gia Hung , Gestrich Wolfgang
Published: August 2005

For water saturated tri‐n‐butyl phosphate (TBP) and for solutions of nitric or nitrous acid therein, the density, viscosity, physical solubility of nitric oxide (NO) and phase equilibria with aqueous phase, as distribution coefficients and water content of the TPB‐phase, were determined. The diffusion coefficient of nitric oxide was calculated, considering the solvent mixture to consist of one, two or, in the presence of nitric acid, three components.
Exergetic and engineering analyses of sulphuric acid decomposition process
Authors: Hammache Abdelaziz , Bilgen Earl
Published: August 2005

The purpose of this study was to evaluate the exergetic efficiency of the sulphuric acid decomposition process, which occurs in hydrogen producing thermochemical cycles and chemical energy storage systems. It is a process in which sulphuric acid is decomposed to a gaseous mixture consisting of water, sulphur dioxide and oxygen, using high temperature thermal energy, oxygen as a vector and mostly adiabatic equipment. Parts of the basic process with excessive exergy losses have been identified and a modified flow sheet has been developed and analyzed from thermodynamic and engineering points of view. Thermodynamic analysis of the modified flow sheet indicates that the overall exergetic efficiency of the decomposition process is 79.86%, which represents an improvement of 14.17% over the basic process. Engineering analysis of a plant producing 106 mol of SO2 per hour shows that the typical levelized cost of chemical exergy production was $ 2.25/GJ exergy from the basic process and $ 1.79/GJ exergy from the modified process.
Determination of process parameters and modelling of lipase‐catalyzed transesterification in a fixed bed reactor
Authors: Jung Hans Jürgen , Bauer Werner
Published: August 2005

Chemical transesterification is of major importance to the edible oil industry. While alkali catalysts randomize all the fatty acids in a triglyceride mixture, the use of a 1,3 specific lipase causes a more selective exchange of fatty acid residues. Basic process parameters for the development of a continuous solvent‐free process in a fixed bed reactor have been determined. The kinetics of the transesterfication reaction and the influence of particle diameter, substrate and water concentration on the effective reaction rate were examined in batchwise experiments. Residence time distribution and parameters of inter‐ and intraparticle mass transfer were determined by modelling of experiments carried out in a fixed bed reactor under transient conditions. Fixed bed reactors with side stream analysis were used for continuous transesterification. A kinetic model was developed for the enzyme catalyzed reaction, thereby showing the analogy between heterogeneous catalytic and enzyme catalyzed reactions. A one‐dimensional heterogeneous reactor model was formulated on the basis of the kinetic equation and different process parameters. For numerical calculations, an exponential enzyme distribution inside the carrier was assumed. The simulation of experimental results indicates that they are well described by the developed model. Water concentration and presence of other substances strongly influence the stability of the immobilized enzyme.
Propylene polymerization — a computer efficient algorithm with orthogonal collocation
Authors: Sarkar Priyabrata
Published: August 2005

This paper presents a new approach to the modelling of solid catalyzed Ziegler‐Natta polymerization of propylene, using orthogonal collocation technique. It is shown that this model can predict the width of the molar mass distribution (MWD) of the product polymer. Its computation time is much shorter compared to other models. An interesting feature of the model is that it considers the discrete nature of the microcatalyst particles and takes advantage of solving a smaller number of stiff differential equations by choosing the number of internal collocation points judiciously. In addition, pseudo‐steady state approximation (QSSA) is applied to some of the moment generating equations.
Multicomponent‐liquid‐membrane permeation of organic acids
Authors: Reisinger Hubert , Marr Rolf
Published: August 2005

The parameters of lactic acid separation from fermentation broths by Emulsion‐Liquid Membranes (ELMs) have been optimized. Using these parameters, lactic acid can be separated up to 90%, concentrated up to 3 times and cleared of most of its by‐products. Only about 1% of glucose and amino acids is permeated together with the lactic acid. With these parameters, not only lactic acid but also other monocarboxylic acids can be separated, the better and faster the lower the pKa‐value of the acid the fewer polar side groups it carries. When separating dicarboxylic acids, the mass transfer is hindered by the second carboxylic group. The smaller the distance between the two carboxylic groups, the slower is the separation of the acid. When several organic acids are separated from the same fermentation broth, their mutual influence is not very strong, at least when the concentrations of the acids are about 100 mmol/l. However, sulphuric acid which is added to the fermentation broth throughout permeation to maintain the broth at a constant pH, does exert a strong influence. In order to reduce the competition between the organic and sulphuric acids during permeation to a minimum, as little as possible sulphuric acid is used. However, a certain quantity of sulphuric acid is necessary to maintain the pH of the fermentation broth during permeation at 4.5, otherwise organic acid separation would become too slow.
Problems in use of supported liquid‐phase catalysts in fluidized bed reactors
Authors: Brüsewitz Rainer , Hesse Diethard
Published: August 2005

Since SLP catalysts can become irreversibly deactivated due to evaporation of the solvent used to prepare the contacts, a saturation technique is proposed to stabilize the catalysts' activity. Application of this technique requires isothermal reaction conditions which can be achieved directly in fluidized bed reactors. Although the fluidization properties of SLP catalysts are mainly determined by interparticle forces, it can be shown that this type of reactor is suitable for an SLP‐catalyzed gas reaction provided that a number of prerequisites are fulfilled. Taking a hydroformylation reaction catalyzed by an Rh complex dissolved in dimethyl glycol phthalate as an example, it is demonstrated that the activity of the prepared SLP catalyst can, indeed, be stabilized by saturation of the reactant gas mixture with the employed solvent.
Gas‐phase properties in stirred tank bioreactors
Authors: Fischer Joachim , Brüring Stefan , Lübbert Andreas
Published: August 2005

Bubble properties in stirred tank bioreactors equipped with standard radial flow Rushton turbines have been investigated. Bubble velocity patterns within a stirred tank reactor were derived from measured local bubble velocity distributions. Local information on specific interfacial areas, bubble number densities and bubble diameters together with local gas hold‐ups, measured in a model medium at gas flow rates which are employed in practice, is presented. All measurements were performed with two new ultrasound pulse techniques which can be used in model as well as during real cultivation processes.
Fuzzy state estimator for a semibatch copolymerization reactor
Authors: Mahesh M. Muniram , Chidambaram Manickam
Published: August 2005

This work describes the development of a fuzzy estimator for determining copolymer composition (F1) in a semibatch solution copolymerization reactor. Membership functions, fuzzy ranges for input (ζ1 mole fraction of monomer 1 in polymerizing mass) and output (F1 mole fraction of monomer 1 in copolymer) are defined. A fuzzy rule base is constructed relating input to output, based on the operator's knowledge. A defuzzification method is selected and the non‐fuzzy values of F1 are obtained. The results are compared with the actual values of F1 which are obtained by rigorously solving the model equations of the system. The fuzzy ranges and limits for input and output are altered separately so as to test the estimator's performance. Thus obtained standard estimator is tested for other operating conditions. The developed estimator performed well also for wider operating conditions.
The concept of statistical molecular association and its application to reaction kinetics and chemical equilibria
Authors: Gestrich Wolfgang
Published: August 2005

A simple statistical theory of molecular association has been developed, taking into account only the probability of residence of one or more molecules in an association volume. The result is a one parameter model which may be applied successfully to reaction kinetics and chemical equilibria of associated compounds. General concentration time profiles are presented and limiting cases discussed. Usefulness of the principle is demonstrated on experimental results.