bluuebunny/crossref_metadata_2025 huggingface dataset:
Ökobilanzen als Instrument der Produktbewertung
Authors: Klöpffer Walter
Published: December 2004

Ecological Balances as an Instrument for Product Evaluation. The predecessor of today's increasingly important ecological balances was the Limits of Growth Report published by the Club of Rome in 1972. Ecological balances cover mass and energy flows and emissions from the raw materials via intermediates all the way to the end products, as well as waste disposal. This also includes the balance of ecological activity at all stages. The components of ecological balances are goal definition, material balance, action balance, balance evaluation, and optimisation analysis. The advantages of ecological balances are their fundamental acceptance by industry and environmental protection groups, clarity and essentially objective assessment, and the possibility of application to systems, comparison of equivalent products, systems, and services and comparison of null variants. Problems encountered with ecological balances arise, for example, because of frequently inaccessible data basis and because of the system definition.
Radiale Wärmeleitung in durchströmten Schüttungsrohren
Authors: Martin Holger , Nilles Michael
Published: December 2004

Heat Transport to the Wall of Packed Tubes. Radial conduction of heat in packed tubes has a crucial influence on yield and selectivity of many heterogeneously catalyzed reactions. In spite of many years of intensive research in the field, there are still tremendous discrepancies between correlations of different origin. Even the standard model using two constant heat transport parameters, which was introduced in the fifties and has since become most widely accepted, has been controversially discussed and called into question. The unsatisfactory state of the art has been an incentive for several groups of researchers to take up this old topic once again. Three parallel experimental investigations on heat transport with air flowing in packed tubes of similar dimensions, electrically heated, steam‐heated, or water‐cooled, were completed in 1991. Comparative evaluation of the results of these three investigations, together with other data from the relevant literature, now provides the first clear answers to some of the questions so controversially discussed in the past.
Rühreinrichtungen in Schneckendosiergeräten — Wirkung und Auslegungsstrategie
Authors: Vetter Gerhard , Wolfschaffner Hubert
Published: December 2004

Stirring Devices in Screw Metering Equipment – Action and Design Strategy. The accurarcy of metering by screw dosage equipment with or without gravimetric control depends primarily on the flow of material to the discharging screw. In the case of cohesive solids, stirring devices are generally required to prevent bridging. Experimental observations show that flow conditions correlate directly with the intensity of stirring. Mass flow in the metering container and hence optimum constancy of metering are attainable only from certain stirring efficiencies upwards. Cases of interference to metering due to poor flow of solids can be explained and overcome by modified dimensioning. The effects of the principal parameters – geometry and speed of rotation of the stirrer – are studied with the aid of two stirrer configurations – viz. overhead and concentric. Straightforward model calculations provide a mathematical method of estimation for optimum and reliable stirrer dimensioning also applicable to strongly cohesive solids.
Dynamische Belastungen von Zyklonabscheidern bei Anwendung in Blowdown‐Systemen
Authors: Muschelknautz Sebastian , Ruppert Kurt Alfred , Klug Franz
Published: December 2004

Transient Loading of Cyclone Separators on Use in Blowdown Systems. On use of cyclone separators for phase separation in blowdown systems, pressure‐discharge systems, and flaring units, considerable momentary liquid forces are often encountered. Only few details are known about the transient loading and dimensioning of such systems. Thus the behaviour of the entering surge of liquid and its effect on cyclone separators has now been studied experimentally and theoretically. Water/glycerol mixtures of various viscosities were used in these model experiments. After entering the separator the liquid immediately forms a compact wall film. It rapidly expands sideways under the action of the centrifugal force and simultaneously decelerates. A two‐dimensional planar mathematical model serves for stepwise calculation of the experimental results with regard to film extension, deceleration, and the resulting transient forces. The results are summarised in the form of design criteria.
Qualitätssicherung bei der Betreuung und Instandhaltung von Anlagen
Authors: Brunberg Raimund
Published: December 2004

Quality Assurance for the Service and Maintenance of Chemical Plants. The production facilities must be incorporated into the quality‐assurance system in order to comply with the requirements of a reproducible high product quality. All activities relating to this subject are combined in the “Anlagenwirtschaft”; this discipline stays with the production facility throughout its entire life‐cycle. Attention is focussed on maintaining and improving the production facility during its useful life in several ways, i.e. in terms of quality of the goods produced as well as the production facilities and their components. A system of hierarchically, clearly structured and identified plant components is the prerequisite for this work and for a complete technical documentation of all activities. Supplementary means and tools to effectively master this task are available. They may be of a technical or of an administrative nature.
Heuristisch‐numerisches Beratungssystem für die Reaktorauswahl bei der Verfahrensplanung
Authors: Dröge Thomas , Schembecker Gerhard , Westhaus Ulrich , Simmrock Karl Hans
Published: December 2004

A Heuristic‐Numerical Advisory System for the Choice of Reactors in Process Design. Since it has become apparent that neither expert systems nor numerical calculations alone satisfy requirements placed on them in the search for the most suitable industrial reactor, a new type of system, viz. the heuristic‐numerical advisory system, was developed. It utilises both knowledge‐based techniques (production rules and/or frames) and the wide range of calculation tools available in chemical reaction engineering, which are addressed via interfaces. In this way it has become possible to obtain very early reliable information about the later design of an appropriate industrial reactor.
Simulierte Gegenstromchromatographie
Authors: Deckert Petra , Arlt Wolfgang
Published: December 2004

Simulated Countercurrent Chromatography. This paper reviews simulated countercurrent chromatography, a separation process that has received only little attention. In contrast to standard batchwise operated chromatography, a periodical mode of operation is used. The feed and collection lines are shifted along the column, thus simulating countercurrent operation of the liquid phase and the stationary solid phase. As a result, higher product yield and higher product purity are obtained. At the same time the amount of solid phase and solvent phase required in comparison to discontinuous chromatography is reduced. Industrial applications have been developed since 1964 by Universal Oil Products (UOP). Large scale separation processes in the petrochemical and the sugar industries are already in operation. On the bench scale this process is used to separate biotechnological products and pharmaceuticals. The need to solve difficult separation problems (isomeric or racemic mixtures, biomolecules, polymers) will encourage further developments. Together with improved process‐simulation tools and process control, simulated countercurrent chromatography will be established as a powerful separation technique with widespread industrial applicability.
Konzept zur Maßstabsübertragung beim Suspendieren im Rührbehälter
Authors: Kraume Matthias , Zehner Peter
Published: December 2004

Concept for Scale‐up on Suspension in a Stirred Tank. The relationships derived for the suspension of solids in a propeller loop can be applied to corresponding processes in a stirred tank by means of analogy considerations. Accordingly, the ratio of stirrer power to slip power of laminar flow state is inversely proportional to the vessel diameter. In contrast, the power ratio remains constant in turbulent flow. There is a pronounced transition range between these two limiting states. The author's own experimental studies performed over a wide range of Re numbers for the recycling flow confirm this relationship. The observations presented explain why numerous authors have determined scale‐up rules lying between these two extremes. The experiments shows that the power input for suspension is always significantly greater than the slip power. Under otherwise identical conditions, the necessary stirrer power is smaller by a factor of three for a propeller stirrer than for a disk impeller. The suspension of small solids concentrations can also be approximated by the flow model presented. The somewhat different physical relations valid in this case are substantiated by the author's experiments. The model also provided information relevant to scale‐up when the particle properties are unknown. This is demontrated for an example in a 21 m3 vessel.
Rückvermischung in Blasensäulen mit Einbauten
Authors: Berg Stefan , Schlüter Stefan
Published: December 2004

Back‐mixing in Bubble Columns Fitted with Internals. Interals installed in bubble column reactors serve mainly for heat transfer and for influencing (suppressing) liquid circulation. Reinforcement of mixing is observed for experimentally for internals subjected to longitudinal flow, which is attributable in limitation of transverse exchange and the resulting increase of axial eddy dimensions. The experimental findings can be readily described by the axial dispersion model for uniform cross sections and equations are given for estimating the dispersion coefficients of the gaseous and liquid phases as a function of the central liquid circulation velocity. Internals subjected to transverse flow hinder the establishment of a large scale circulatory motion and therefore suppress mixing on the bubble column. Two calculation procedures of differing model depth are presented which permit determination of concentration and temperature profiles in bubble column reactor cascades. Moreover, equations are given for estimating reflux conditions on sieve plates and bundled tube heat exchangers in cross flow which are based on experimental investigations.
Mathematische Modelle der morphologischen Entwicklung von myzelförmig wachsenden Mikroorganismen
Authors: King Rudibert
Published: December 2004

Mathematical Models of the Morphological Development of Mycelium‐Forming Microorganisms. A significant proportion of the products produced by biotechnology come from mycelium‐forming microorganisms. The highly complex growth and product formation behaviour of these organisms places special demands on process control and on reactor design. This article demonstrates the possible contribution of mathematical models. Particular attention is directed to morphological aspects of an important class of organisms, viz. streptomyces.
Inertgaseinsatz in Füllkörperkolonnen für die Flüssig/Flüssig‐Extraktion
Authors: Braun Christopher , Billet Reinhard
Published: December 2004

Gas is fed into static countercurrent extractors with the goal of introducing more energy into the binary liquid/liquid system. Increasing the turbulence raises the particle dispersion and thus increases the mass transfer area. This in turn should lead to improved mass transfer. Decision aids for more or less promising use of inert gas in liquid/liquid extraction are presented on the bases of recent publications and the authors' own studies and correlations.
Mini‐Technikumsanlage für Hochdruck‐Polymerisationen bei kontinuierlicher Reaktionsführung
Authors: Buback Michael , Busch Markus , Lovis Kai , Mähling Frank‐Olaf
Published: December 2004

Miniaturisierte Apparaturen als Nachbildung kompletter Produktionsanlagen sind für die Entwicklung neuer oder die Modifikationen bestehender Verfahren von besonderem Interesse. In dieser Arbeit soll eine Anlage vorgestellt werden, die es erlaubt, Hochdruck‐Polymerisationen bei kontinuierlicher Betriebsweise durchzuführen. Sie ist vor allem für Reaktionen mit Ethen konzipiert und bietet die Möglichkeit, Homo‐ und Copolymerisationen bei photochemischer Initiierung, etwa mit Excimerlaser‐Licht, sowie auch bei chemischer und bei spontaner (thermischer) Initiierung bei Drucken bis 3000 bar und Temperaturen bis 300 °C auszuführen und detailliert zu studieren [1].
Bestimmung der Schalleistung von Zentrifugen über Schallintensitätsmessungen
Authors: Stelter Peter , Harms Andreas
Published: December 2004

The sound pressure level measured at a distance of one meter is frequently used to assess the sound emission of a machine. The sound pressure level depends on the measuring distance, the directivity pattern, if any, of the machine and on the sound‐absorbing properties of the place of installation. Because it is a local field parameter it is not very suitable for ascertaining the sound emission of a machine. In contrast to, the sound power level is far more suitable because the influence mentioned earlier can be corrected and the value is reproducible for any random test condition. Generally, it is calculated from the results of sound pressure level measurements by application of the standardised enveloping surface method. Concerning sound intensity measurements a special probe allows ascertainment of the sound intensities directly on the enveloping surface. Despite an initially elaborate measuring technology, this method is in fact often faster and more exact than the enveloping surface method because it does not require subsequent correction to determine the sound power level. The benefits and drawbacks of sound pressure and sound intensity measurements are compared with each other on the basis of measurements on centrifuges directly related to practical operation.
Entwicklungstendenzen bei der Partikelabtrennung aus Gasen mit filternden Abscheidern
Authors: Schmidt Eberhard
Published: December 2004

Cleanable surface filters are used as highly efficient separation devices for removing particles from gases in three major areas of application, viz. reduction of emissions, product recovery, and process gas purification. In order to utilize their excellent separating properties in processes where unfavorable operating conditions mean that competing kinds of separators have hitherto been used, filtering separators are undergoing constant development. This paper presents and discusses future‐oriented developments from current work and completed plant in the three areas of ‘modeling/computer simulation’, ‘filter medium development’, and ‘crude gas conditioning’.
Praxisbezogenes Vorgehen bei der Auslegung von Sicherheitsventilen und deren Abblaseleitungen für die Durchstroömung mit Dampf/Flüssigkeits‐Gemischen – Teil 2
Authors: Schmidt Jürgen , Westphal Frank
Published: December 2004

The design of an integral safety valveblow‐off pipe system embraces the following essential steps: 1. An incident scenario must first be defined. All reasonable deviations from proper operation of plant must be considered. 2. The flow state at the entry to the safety valve must then be ascertained (one‐phase or binary flow); and 3. the minimal mass flow from the plant component to be protected must be calculated. Independently thereof, it is necessary 4. to determine the mass flow density in the blow‐off pipe system; it is usually related to the cross‐sectional area of the valve seat. The ratio of the two quantities gives the minimum necessary blow‐off cross‐sectional area. 5. In the final step, the pressure drop in the feed line and the counter‐pressure at the valve exit must be examined in order to assure reliable functioning of the valve also in conjunction with the pipe system. Steps 1. to 3. were considered in Part 1, and steps 4. and 5. are described herein. Appropriate recommendations and the necessary equations are given for each step. The main emphasis is placed on applicability of the calculations.
Gasinduziertes Einmischen von Reaktionsstoppern in Behälter mit niedrigviskosen Flüssigkeiten
Authors: Schimetzek Ralf , Pfleger Dirk , Ulonska Armin
Published: December 2004

These studies consist of experiments, physical modelling, and numerical simulations concerning gas‐induced injection and mixing of reaction inhibitors in vessels containing low viscosity liquids. The mixing times required to achieve a final mixing quality of 95% were determined by means of a decolorization technique and a probe method (conductivity probes). The mixing time decreases with increasing gas flow rate, liquid level, eccentricity of the gas injection point, and with decreasing liquid viscosity. Based on fundamental physical principles, analytical models were developed which can be used to estimate, with an average precision of ± 13 %, the mixing times measured on three different scales. The results of scale‐up were additionally confirmed via numerical simulations. The results of these studies show that gas‐induced mixing of reaction inhibitor solutions can represent a reliable safety system for preventing exothermal runaway reactions. Moreover, direct injection of gas may also be used for admixing additives during normal operation of reactors and storage tanks.
Messung der dynamischen Grenzflächen‐spannung im System wäßrige Tensidlösung/organisches Lösungsmittel
Authors: Miller Reinhard , Ferrari Michele , Ravera Francesca , Liggieri Libero , Zholob Sergej A. , Fainerman Valentin B. , Neumann A. Wilhelm
Published: December 2004

Dynamic interfacial tensions provide insight into the mechanism of surfactant adsorption at and transport across an interface. As an example, the adsorption kinetics and the distribution of a surfactant (alkyl dimethyl phosphine oxide with an alkyl chain length of 13) was studied at the water/hexane interface. The drop shape method used yields dynamic interfacial tensions that pass through a minimum under certain conditions. Model calculations show that depth, width and location of the minimum and the equilibrium adsorption state depend on several parameters: the diffusion coefficients of the surfactant in the two liquids, the distribution coefficient between the phases, the liquids volume ratio, and the total surfactant concentration in the system. One can conclude that surfactants are often soluble in both liquid phases, and transfer across the interface between them has to be considered. If a surfactant is to be optimized in a liquid‐liquid system to achieve maximum efficiency of a technological process, the surfactant distribution coefficient plays a significant role.
Chemisches Recycling von Kunststoffen
Authors: Sasse Frank , Emig Gerhard
Published: December 2004

On completion of the first life cycle of plastics various recycling processes are available for further utilization of these evaluable materials. The choice of process will depend upon the materials to be recycled. In chemical recycling polymers are degraded to basic chemical substances which can be reused in the petrochemical industry. This route plays a key role for soiled waste plastics or waste plastics which could not hitherto be recycled. The pyrolysis of acrylic polymers provides a good basis for comparing a fluidized bed reactor and a tubular reactor with regard to reactor modelling. The tubular reactor with internal mass transport is a simplified model for a rotary kiln. Parameters relevant for reactor design and scale‐up are presented.
CAE‐Systeme für die Prozeßleittechnik
Authors: Ahrens Wolfgang
Published: December 2004

CAE systems for the workings of chemical engineering plant have reached a high level of functionality and system architecture. This also applies to process control systems. What is now needed is the integration of the different systems in order to avoid unnecessary duplication of effort, data inconsistency, and time wastage. Fortunately, there are various approaches permitting such integration. Starting from the underlying system architecture this paper therefore presents a variety of integration concepts. Some of these are propriety solutions because they are based on various manufacturers' products. However, STEP and CORBA also involve standards‐based technologies. The time required for their realisation is better estimated in years.
Qualitätsmanagement bei der Herstellung von Chemieapparaten aus Sonderwerkstoffen
Authors: Renner Michael , Lorsbach Birgit , Schumacher Kurt
Published: December 2004

Quality Management during the Fabrication of Chemical Equipment Made of Special Materials Optimizing a material's resistance to corrosion by the addition of alloying elements up to their solubility limits will make it increasingly difficult to use these frequently unstable alloys for the manufacture of chemical plant. The requirements these materials have to meet in the manufacture of chemical plant in terms of manufacturing technology and quality management, are becoming increasingly stringent. The current situation, for example in the manufacture of domed heads of pressure vessels, forgings, heat exchangers, and filter screens with a high specific surface area as a constituent part of stirred suction filters using advanced metallic materials, is not very satisfactory. Results of fabrication tests necessary for pressure vessel manufacture as well as in‐service failures frequently demonstrate insufficient expertise of workshops dealing with high‐alloy stainless steels and nickel‐based materials. That the in‐service failure of compoents clearly leads to considerable costs due to maintenance, delays in supply, and production downtimes. The economic consequences can be substantial. The aim of this paper is to highlight sensitive areas by demonstrating the impact of unintentional and unnoticed fabrication‐related changes in welding parameters and to provide information on easily applicable methods of monitoring techniques.
Feststoff‐Bioreaktoren – Teil 1: Stationäre Anlagen
Authors: Vollbrecht Dietmar
Published: December 2004

Solid State Fermentation‐Bioreactors – Part 1: Stationary Types. After World War II, solid state fermentations (SSF) in automated facilities developed rapidly in East Asia countries, especially Japan, to achieve a present annual market volume of about $ eight billion. In contrast, SSF, after having been introduced in Western countries at the onset of this century, became almost completely neglected. The comparative ease of running SSF bioreactors and in particular their low processing costs and considerably higher yields in comparison with submerged fermentation (STF) suggest that this technology might have great economic importance in producing food and pharmaceutically valuable substances such as antibiotics, anti‐carcinogenic substances, antioxidants, flavors, fragrances, health foods, hypocholesterinemic agents, pigments, starter cultures, protein‐enriched feed, thrombolytic enzymes, vasoactive agents, vitamins etc.
Einsatz von Pervaporation‐Bioreaktor‐Hybridprozessen in der Biotechnologie
Authors: Lipnizki Frank , Hausmanns Stephan , Laufenberg Günther , Field Robert , Kunz Benno
Published: December 2004

Use of Pervaporation/Bioreactor Hybrid Processes in Biotechnology Pervaporation is a membrane separation process with considerable innovative possibilities in the area of biotechnology. Above all, the combination of bioreactor and pervaporation has potential in the longer term as an alternative to conventional batch processes. This article considers the state of the art of pervaporation/bioreactor hybrid processes. The possible applications of such hybrid processes are discussed and compared with conventional processes. It becomes apparent that the use of pervaporation/bioreactor hybrid processes can avoid product inhibition and greatly enhance the productivity of biotechnological processes.
Nanofiltrationsmembranen für Trennprobleme in organischen Lösungen
Authors: Schmidt Matthias , Mirza Sohail , Schubert Rolf , Rödicker Em. Herbert , Kattanek Siegfried , Malisz Jaček
Published: December 2004

Nanofiltration Membranes for Separation Problems in Organic Solutions.

Nanofiltration based on rejection and flux features intermediate between those ultrafiltration and reverse osmosis is one of the technically and scientifically interesting membrane processes with a great future. Moreover, most commercial available nanofiltration membranes are only suitable for separation processes in aqueous solutions. A small number of composite membranes with a highly cross‐linked selective layer show a technically interesting resistance towards organic solvents, such as ketones, esters, ethers or alcohols. The present article describes such nanofiltration membranes used for separation of low molecular weight chemical compounds from polar or nonpolar solvents, but also for the removal of organic compound from aqueous solutions. Methods of manufacturing and modifying such solvent stable composite membranes are shown, as are the conditioning of membranes and examples of industrial application.
Feststoff‐Bioreaktoren — Teil 2: Bewegte Anlagen
Authors: Vollbrecht Dietmar
Published: December 2004

Solid State Fermentation Plant ‐ Part 2: Non‐Stationary Units.

Western experience with solid state fermenters in which the fermenting substrate is circulated is still limited to the laboratory scale (< 20 kg of substrate). In contrast, automated industrial plant with capacities of 10 to 100 t of inoculated substrate per charge have been in operation in Japan for several decades for the semi‐continuous production of enzyme mixtures. However, the substrate is only occasionally circulated in these plant. It is shown from the literature cited that stationary solid state fermentation processes employing the tablet method give significantly better results (lower plant costs, shorter process duration, high enzyme product yields, higher product quality, less pronounced gradient formation, etc.) than processes with occasional product circulation. Stationary solid state fermentation plant (tablet method) therefore appear to represent the method of choice, especially for the production of secondary metabolites, pigments, flavours, etc., whose production optima lie within fairly narrow limits which cannot be met by non‐stationary units.
Gasinduziertes Einmischen von Reaktionsstoppern in Behälter mit höherviskosen Flüssigkeiten
Authors: Schimetzek Ralf , Ulonska Armin
Published: December 2004

Gas‐Induced Admixture of Reaction Inhibitors in Vessels Containing Liquids of Higher Viscosities.

This article deals with calculation of the mixing action of gas introduced close to the bottom of vessels containing viscous liquids ( > 10 mPa s). The mixing time required for 95% mixing was determined. This time decreases with increasing volume flow of gas and level of liquid, increasing eccentricity of the point of gas introduction, and decreasing liquid viscosity. With the aid of an analytical model based on fluid dynamics, the mixing time to be expected can be predicted up to – and presumably beyond – a viscosity of 350 mPa s. Only a slight increase in mixing time is to be expected with decreasing interfacial tension and in systems with inhibited coalescence. The results show that gas‐induced mixing of vessels [1–4] is also applicable to high‐viscosity liquids. The approach can also be used for purposes other than admixture of reaction stoppers, such as the admixture of additives in normal operation of reactors and storage tahks.
CAPE in der Praxis — Möglichkeiten und Grenzen aus Nutzersicht
Authors: Lohe B. , Bessling B. , Schoenmakers H. , Scholl S. , Staatz H.
Published: December 2004

CAPE in Practice ‐ Opportunities and Limits from the User's Point of View.

CAPE tools comprise computer based tools and methods for the design of chemical processes ‐ the use of which is indispensable in modern chemical engineering. This paper discusses the degree to which CAPE is already applied and whether limitations exist. Within BASF, the CAPE framework is provided by the “ProcessNet”, which integrates numerous simulation and design tools. The engineer relies alternatively on inhouse or commercial software. The advantage of CAPE in terms of efficiency depends not only on complex programs, but also to a large extent on the multiple use of intermediate data and program modules. The ProcessNet also features a hierarchical file structure to support the engineer's desktop management. The CAPE environment is being continuously improved. The main constraints on CAPE today are, for example, the missing link between fluid and solid applications, a deficit in data management and the poor state of development of advanced or special programs. The progress of research in this area is followed with great interest.
Systematische vergleichende Kostenanalyse von destillativen und extraktiven Stofftrennverfahren
Authors: Glanz Stephan , Blaß Eckhart , Stichlmair Johann , Punin Anatoli , Balagula Ilja , Victorov Valeri
Published: December 2004

Systematic Comparative Cost Analysis of Separation Processes Based on Distillation and Extraction.

Rectification is the most commonly used but not always the most economical method of thermal separation. Above all in the case of closely boiling mixtures it becomes very demanding with regard to both equipment and energy. It is often possible to replace rectification by another energetically more favourable separation process such as liquid‐liquid distillation, decantation, or absorption. Owing to the resulting wealth of possibilities for the separation of a mixture it is desirable to gain further knowledge about the economics of individual processes and about the selection of suitable entrainers under given conditions.
Rührtechnik am Ausklang des 20. Jahrhunderts
Authors: Zlokarnik Marko
Published: December 2004

Mixing at the End of the 20th Century In the light of the rapid and highly successful development of mixing technology during the past 50 years the author presents a terse and critical assessment focussing on open problems and their possible solutions. One of the shortcomings encountered in practice lies in the failure to distinguish between micro‐ and macro‐mixing as fundamental mixing processes. The other concerns the failures attributed to dimensional analysis which actually originate in inappropriate measuring and application techniques.
Floating zone growth of CuO under elevated oxygen pressure and its relevance for the crystal growth of cuprates
Authors: Behr G. , Löser W. , Apostu M.‐O. , Gruner W. , Hücker M. , Schramm L. , Souptel D. , Teresiak A. , Werner J.
Published: December 2004

CuO single crystals have been grown from the melt by a floating zone method with optical heating at elevated oxygen pressures 3.5 to 5.5 MPa and growth rates as high as 10 mm/h. Melting experiments and recalculated Cu‐O phase diagram data show that CuO melts incongruently. The melting temperature increases and the concentration difference between the melt and the CuO phase decreases for rising oxygen partial pressure. Accordingly, increasing the oxygen partial pressure improves the growth process by reducing both the significant oxygen loss during melting as well as the composition difference at the growth interface. The results on CuO provide important information for the crystal growth of more complex cuprates. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In situ X‐ray analysis of MoO3 reduction
Authors: Leisegang T. , Levin A. A. , Walter J. , Meyer D. C.
Published: December 2004

The reduction of MoO3 to MoO2 under hydrogen/argon atmosphere (5 vol. % H2/95 vol. % Ar) in the temperature range 323 K…623 K was studied in situ by means of wide‐angle X‐ray scattering. It has been found that the starting material, MoO3, consists of two different orthorhombic MoO3 phases A and B with nearly the same structure parameters. The phase A (fraction of 37.1 wt%) describes the larger crystallites whereas the phase B (fraction of 62.9 wt.%) describes the smaller crystallites. Under the reduction to monoclinic MoO2 phase during the heating, the thermal evolution of the phase fractions is different. A conclusion is drawn that MoO2 is formed preferably in big crystallites. About 10 wt. % of MoO2 has been found to form at 623 K resulting in about 69 wt. % after cooling to room temperature followed by holding in Ar/H2 atmosphere about 24 h. Additionally, about 4.4 wt. % of the Mo4O11 oxide probably formed in large crystallites was detected in the reduced powder after the cooling. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Void formation in the Cu layer during thermal treatment of SiNx/Cu/Ta73Si27/SiO2/Si systems
Authors: Hübner R. , Reiche R. , Hecker M. , Mattern N. , Hoffmann V. , Wetzig K. , Heuer H. , Wenzel Ch. , Engelmann H.‐J. , Zschech E.
Published: December 2004

The thermal stability of a SiNx passivation layer and its influence on the annealing behavior of an amorphous Ta73Si27 diffusion barrier deposited between copper and SiO2 were analyzed by X‐ray diffraction, glow discharge optical emission spectroscopy, Auger electron spectroscopy, scanning electron microscopy, and transmission electron microscopy. During heat treatment at a temperature Tan = 500 °C, diffusion of Cu atoms out of the Cu metallization into the SiNx passivation occurs. The Cu diffusion intensifies with increasing annealing temperature and annealing time and seems to be a necessary precondition for a defect formation process observed within the Cu metallization. Depending on the chemical composition of the SiNx/Cu interface, voids in the μm‐range can be formed within the Cu film. Compared to an unpassivated sample, heat treatment leads to a reduced diffusion of Ta atoms from the barrier through the copper into the SiNx/Cu interface. The barrier crystallization process into Ta5Si3 occurring during annealing at Tan = 600 °C is principally not affected by the presence of a SiNx passivation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Raman spectroscopic and X‐ray investigation of stressed states in diamond‐like carbon films
Authors: Krawietz R. , Kämpfe B. , Auerswald E. , Brücher M.
Published: December 2004

The non‐destructive characterization of intrinsic stress is very important to evaluate the reliability of devices based on diamond‐like carbon (DLC) films. Whereas the only requirement for the X‐ray diffraction method is a crystalline state of specimen, Raman spectroscopic stress analysis is restricted to materials showing intensive and sharp Raman peaks. On the other hand, Raman spectroscopy offers the possibility to measure stress profiles with lateral resolution of about 1 micron. The results of stress measurements in DLC films using both X‐ray diffraction and Raman spectroscopy are found in very good correspondence. Mean stress in carbon films consisting of very small crystallites on silicon substrates has been determined by measuring and fitting the stress profiles in the substrate near artificial vertical film edges. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Demonstration of the effect of softening and fire resistance of materials on burning characteristics
Authors: Paul K. T.
Published: December 2004

An important observation during full‐scale fires was that burning behaviour is often determined by softening characteristics as well as ignitability, flame spread, etc. Examples include stacking chairs where thermoplastics give a rapid rate of fire growth and suspended ceilings where thermoplastics reduce fire hazard. A test rig has been progressively developed at RAPRA to reproduce the mechanisms and fire growth rates of stacked chairs and to evaluate the role of softening in fire growth. Although the ignitability of fire‐retarded materials is less than that of non‐fire‐retarded grades, the fire growth rate in stacks is similar and may be related to the softening behaviour determined by exposing sheets of material to radiant heat. The rate of fire growth in stacks may be significantly reduced by modifying the softening behaviour of materials, e.g. by using asbestos‐reinforced thermoplastics which can form an integral, non‐melting felt or by using non‐melting materials such as SMC or wood.
A new approach to testing materials in the NBS smoke chamber
Authors: Routley A. F. , Skipper R. S.
Published: December 2004

The standard NBS/Aminco smoke test chamber is critically examined from the point of view of repeatability and reproducibility of the apparatus itself. Individual components contributing to the overall determination are examined and suggested lines for improvement are made which should result in more consistent results. Problems associated with the presentation of results are discussed and a new approach which includes time‐weighted data is proposed. This attempts to consider the rate dependence of smoke production in one calculated figure rather than isolated observations such as maximum optical density. Utilizing the NBS/Aminco chamber, a novel procedure for determining the smoke evolution characteristics of materials has been developed which can be considered to simulate more closely the progress of thermal degradation that a material undergoes in a real fire.
Mathematical modeling of natural convection in fire—A state of the art review of the field modelling of variable density turbulent flow
Authors: Kumar S.
Published: December 2004

This review concerns the mathematical modeling of fire phenomena. The fire is treated as a head and mass source driving a fluid flow process. Combustion is not included. It deals in detail with the field modeling approach incorporating the effects of turbulence, strong buoyancy and variable density on the transport of momentum, heat and mass. For the sake of simplicity, other effects such as those due to the interactions of the above mechanisms with the wall, radiation, etc., which may be crucial to the dynamics of the fire phenomenon, are not dealt with in this review. These effects will be the subject of future work.
Raman spectroscopy in the analysis of fire gases
Authors: Alden M. , Blomqvist J. , Edner H. , Lundberg H.
Published: December 2004

Raman scattering is a possible technique for analysing gas mixtures. In the work here described Raman scattering was used for detection of gases extracted from different model fires, where wood, polymethylmetachrylate (PMMA) and polystyrene were used as test materials. Raman spectra of gas samples from differently ventilated model fires are presented as well as the variation of O2, CO2 and CO concentrations as a function of time with an effective time constant of less than 5 s. The sensitivity of the experimental set‐up was estimated to be about 1000 ppm, but suggestions are given how to reach a detection limit of about 1 ppm. The feasibility of the technique and various ways of improving it are briefly discussed.
Heat transmission of proban®‐treated fabrics subjected to a radiant heat source
Authors: Stephenson J. E.
Published: December 2004

The apparatus described in DIN 4842 was used to measure the heat transmission of a series of Nomex, polyester–cotton, Proban®‐Treated cotton, untreated cotton and wool workwear fabrics subjected to a radiant heat source. Heat transmission was found to be dependent on the incident heat flux, fabric weight and fabric thickness. At the heat flux levels tested, 10 KJ m−2s−1 and 20 KJ m−2s−1, heat transmission was found to be largely independent of the fibre composition of the fabric when single layers of fabric were tested. The level of heat transmission was reduced by the use of multiplayer assemblies or a reflective aluminium coating, but the greatest reduction was obtained when air spaces were interposed between the fabrics. Conbinaitons of fabrics were developed which transmitted less than 205 KJ m−2s−1 during testing at incident heat flux levels of 10 KJ m−2s−1 and 20 KJ m−2s−1.
Simultaneous thermal analysis (STA) of dielectric materials
Authors: Stevens G. C.
Published: December 2004

Polymeric Dielectrics are usually chemically complex, and it is attractive to establish techniques capable of providing a general assessment of material composition and thermal behaviour. Simultaneous thermal analysis (STA) is capable of providing such an assessment and complementing flammability studies. The use of STA in both of these roles is demonstrated for a number of polymer materials used in high‐voltage cables. The materials investigated include various polyethylenes, ethylene‐copolymers and filled polyvinylchloride formulations. Fingerprint identification of materials and the influence of chemical structure and additives on thermal behaviour is discussed. In particular the influence of antimony trioxide‐chlorinated hydrocarbon flame retardants is examined. The application of STA information in guiding flammability studies is shown by example, and some potential routes for further development are also discussed.
Why it is difficult to measure the burning characteristics of materials and products
Authors: Rieber Martin
Published: December 2004

Flammability tests are difficult because of the complexity of burning processes and of safety considerations. Experimental fires only give a partial view of the combustion process. Owing to the dynamic processes occurring in the flame, tests are very sensitive to external influences. Use, therefore, of flammability test methods should be made only with a clear understanding of what is being tested. Only officially standardized and recognized test methods should be sued.
An investigation of fire plume impingement on a horizontal ceiling. 1—Plume region
Authors: You H.‐Z.
Published: December 2004

A theoretical and experimental study of buoyant, axisymmetric, turbulent, diffusion flames is described. Measurements included profiles of mean velocity, mean temperature and mean concentrations of major species for flames having heat release rates of 1.67 and 8.51 kW. An integral model was developed and calibrated with both present and earlier measurements. Empirical constants account for flow entrainment and rates of fuel consumption. Overall, the integral model provided satisfactory predictions of bulk velocity, temperature and concentrations in both combusting and non‐combusting plumes.
An investigation of fire‐plume impingement on a horizontal ceiling. 2—Impingement and ceiling‐jet regions
Authors: You H.‐Z.
Published: December 2004

A theoretical and experimental study of ceiling flows induced by both impinging fires and weak plumes on a horizontal ceiling is presented. Measurements along a ceiling radius were made of impinging diffusion flames with heat‐release rates of 1.67 and 8.51 kW, resulting in convective and radiative ceiling‐heat fluxes, radiant heat flux to the surroundings and profiles of mean velocity, mean temperature and mean concentrations of major species. However, only ceiling heat fluxes were obtained for weak plumes of pre‐mixed flames of 0.24, 0.385 and 0.709kW. The predicted ceiling convective heat fluxes by an integral model are in good agreement with the measured values. In general, the present model also provides satisfactory predictions of flow thickness, bulk velocity, temperature and gas concentrations for both impinging fires and weak plumes.
Smoke and toxicant production during thermal degradation
Authors: Alexeeff George V.
Published: December 2004

A series of materials were tested in a radiant furnace for their production of toxicants (carbon monoxide and hydrogen chloride) while concurrently measuring the weight remaining of the test specimen. In addition, the effect of sample form on toxicant production was considered for Douglas fir and polyvinyl chloride. The smoke‐exposure profile was found to be dependent on the material's form. The specimen‐irradiation time and the incident heat flux. The calculation of exposure using a Ct product based on the area under the production curve was found useful for smoke and toxicants. Concentrations of toxic gases produced were not linearly related to sample‐weight loss throughout the experiments. The influence of sample form on smoke and toxicant production was greater for Douglas fir than for polyvinyl chloride. The results indicate that in toxicity tests samples should be tested in their end‐use form and that a material's thermal properties may influence toxicity‐value calculations.
Fire‐performance of a ventilated facade insulated with a B2–classified rigid polyurethane foam
Authors: Jeffs G. M. F. , Klingelhöfer H. G. , Prager F. H. , Rosteck H.
Published: December 2004

A two‐storey test rig was used to investigate how an insulated facade would react to the impingement of a simulated room fire. In particular, whether or not a facade insulated with polyurethane foam would promote vertical flame spread. Wooden cribs weighing 40 kg were used as fire sources. One set of tests was run without any steel cladding to study the behaviour of the polyurethane foam alone. In a wall‐configuration test as well as under a conrner‐configuration one limited vertical and horizontal flame propagation were found. The degree of damage was to some extent, greater under the corner‐test conditions than with the wall tests. A ventilated facade construction with the profiled steel cladding fixed to vertical support‐work was used for the second set of tests. In order to simulate repair conditions, the outer metal cladding was completely removed from the lower 1.5 m of the facade. In Both tests a strong chimney‐effect behind the cladding was observed. This intensification of the flame impingement led to a flame spread up the top of the facade. The tests indicated that the vertical flame spread would continue unless the method of construction incorporated vertical fire stops.
Toxicity and incapacitation due to hydrogen chloride
Authors: Birky Merritt M.
Published: December 2004

Hydrogen chloride is the principal product released during the combustion of poly(vinylchloride). It is classified as a sensory and pulmonary irritant. The toxicity of hydrogen chloride (HCl) has been the subject of numerous acute toxicological studies on rodents to determine the effect of HCl exposure on humans during fires. The lethality studies show that HCl destroys the upper respiratory tract and the eyes of rodents. A few of the rodent studies measured the HCl concentration required to produce incapacitation within a given short‐exposure period. These concentrations were higher than the lethal concentrations due to the fact that most deaths occur post‐exposure. The findings from rodent studies were basically confirmed by exposing non‐human primates (baboons) to high HCl concentrations for 5 min and measuring escape potential. In the baboon study, no statistical significance could be found between the time‐to‐effect parameters, failure modes and the HCl concentrations. The relevance of the baboon behavioral model and physiological response to human escape‐potential in a fire environment that contains HCl is questionable. In terms of the behavioral model, the baboons were able to carry out the escape routine with their eyes closed during the exposure. Inability to see was not considered incapacitating. Humans would have great difficulty escaping from a fire with their eyes closed. Furthermore, the baboons escaped by one simple action; jumping out. Most humans could not escape from a fire by one simple, instantaneous act. Based on the review of HCl toxicity and basic toxicological principles, elements required for the development of an appropriate animal incapacitation model for irritants are proposed. Exposure of animals to irritants, such as HCl, will only provide information on human escape impairment from fire when the animal models address the direct result of irritant effects on vision and respiratory function. Most of the preset studies measure the delayed, secondary systemic effects that produce asphyxia. Clearly, the measurement of vision or the lack of vision should be of primary importance in any irritant smoke incapacitation model.