Beurteilungskriterien für sicherheitstechnische Prüfungen

Methods are presented which enable one to assess and compare the hazard potentials of different technical installations without the necessity of a detailed technical plant analysis. The basis is the energy content of the installation. In the case that energies with different impact mechanisms, e.g., pressure and heat, are to be compared, the probit method is used. In addition, the expected frequency of occurrence is included in the assessment. This is an approach which is already used in neighboring countries. It is foreseeable that it will gain importance in Germany as well. In the case of elevators the predator‐prey model is used to analyze the time series of accidents. The influence of errors in inspection and maintenance is put into evidence by comparison with the SIL classification.     

Einfluss der Feuchtebeladung bei der Druckbeanspruchung von Granulaten

The material behavior of γ‐Al₂O₃‐, zeolite 4A‐ und sodium benzoate granules at compression has been experimentally studied. The material behavior has been found to be dominant elastic, elastic‐plastic and dominant plastic. Additionally, the influence of moisture content on the material behavior has been investigated. The force‐displacement curves have been approximated using suitable mechanical models.     

Deactivation of hydrodesulfurization catalysts during reactor startup

Metal sulfide catalysts for ultra-deep hydrodesulfurization of diesel generally lose a fraction of their catalytically active sites during reactor startup. The underlying mechanisms are discussed. A laboratory diagnostic tool consisting of three probe molecules is developed for testing metal sulfide catalysts' start-of-run (SOR) activity maintenance. It is found that a significant fraction of the active sites on a commercial supported catalyst are deactivated permanently, but this is not the case with a bulk metal sulfide catalyst. The SOR deactivation of the bulk catalyst is completely reversible, while that of the supported catalyst is partially reversible. The diagnostic tool may provide a basis for developing a high-throughput approach for evaluating and enhancing catalyst SOR stability, thereby increasing plant productivity.     

Sinterability of Forsterite Prepared via Solid‐State Reaction

In this work, the sinterability of forsterite powder synthesized via solid‐state reaction was investigated. X‐ray diffraction (XRD) analyses indicate that the synthesized powder possessed peaks that correspond to stoichiometric forsterite. Scanning electron micrographs revealed that the powders were formed agglomerates, which were made up of loosely packed fine particles. Subsequently, the forsterite powders were cold isostatically pressed into a disk shape under 200 MPa and sintered in air at temperature ranging from 1200°C to 1500°C (interval of 50°C) with ramp rate of 10°C/min and dwelling time of 2 h. The sinterability of each sintered samples was examined in terms of phase stability, relative density, Vickers hardness, fracture toughness, and microstructural examination. XRD examination on all the sintered samples exhibited pure forsterite, in which the generated peaks were found to be in a good agreement with JCPDS card no. 34‐0189. The densification of forsterite progressed to reach a maximum relative density of ~91% at 1500°C. This study also revealed that high‐strength forsterite ceramic can be synthesized via solid‐state reaction as forsterite attained favorable mechanical properties, having fracture toughness of 4.88 MPam^1/2 and hardness of 7.11 GPa at 1400°C.     

Heißgasfiltration im Synthesegas aus Biomasse

During thermochemical conversion of biological material in a fluidized bed reactor the nutrients are remaining as dust in the product gas. Hot gas filtration represents a possibility to recover these minerals. The characteristics of this gas add up new technical tasks. The following article gives an account of long lasting experience of operation and optimization in a pilot plant.     

Wood‐Plastic‐Composites: Rheologische Charakterisierung und Füllverhalten im Spritzgießprozess

Wood‐plastic composites (WPC) show a complex and completely different material and flow behavior in comparison to pure polymers. Especially the flow behavior is very important for the processing of these composites. In the following article results of rheological characterization and investigations of the filling behavior during the injection molding process are presented. Furthermore, appearing challenges and possible methods of resolution are discussed.     

Aqueous Surfactant Two‐Phase Systems for the Continuous Countercurrent Cloud Point Extraction

Aqueous nonionic surfactant solutions split into two phases if the temperature is increased beyond a certain temperature, the so‐called cloud point temperature. Presently many different types of nonionic surfactants are produced commercially, out of these numerous have been considered as potential solvent for the cloud point extraction. In this work the crucial thermophysical properties of nonionic surfactants are investigated to determine the potential of surfactant systems for extraction processes. Phase equilibria of the binary system Triton X‐114/water and the ternary system Triton X‐114/water/phenol were measured. Based on these data the cloud point extraction was implemented in a continuous stirred extraction column. It was found, that increasing temperature within the column reduces the loss of surfactant and leads to an increasing enrichment factor. This work demonstrates that surfactant/water systems represent a suitable alternative to conventional solvents and can effectively be processed in continuous extraction columns.     

A new inrush detection method for transformer differential protection

Contents The long-used restraining principle, based on the detection of 2nd harmonics in the currents, can not always satisfactorily meet the demand of blocking the transformer differential protection for all three phases, because the line currents are not the direct image of the core saturation. The differential protection may become inadequate. A transformer can however be switched on for all cases, without the false or fail-safe tripping, when the harmonic restraint is derived from the magnetic field strength of the core.If a delta-connected winding is present, the magnetic field strengths can not be easily recognized in the line currents, because their zero-sequence component is distorted. A new method is presented, which can estimate the fundamental and the 2nd harmonic of this zero-sequence component. The components of the magnetic field strength can therefore be determined in currents only, whose ratio is known to be characteristic for the core saturation.The proposed method was implemented on an industrial protection system based on a microprocessor and was tested on data obtained from computer-simulation and a model transformer in a laboratory. It turned out that the proposed method performed well on all cases.

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Eine neue Methode der Einschalterkennung für den Transformator-Differentialschutz

Übersicht Die üblicherweise benützte Blockierung beim Einschalten eines Transformators beruht auf der Bewertung der zweiten Harmonischen in den Strömen. Dieses Prinzip kann nicht immer den Transformatorvergleichsschutz in allen drei Phasen blockieren. Dagegen kann ein Transformator in allen Fällen ohne Fehlauslösung eingeschaltet werden, wenn die Blockierung aus der Harmonischen der magnetischen Feldstärke des Kerns abgeleitet wird.Eine neue Methode wird vorgestellt, wie die Homopolarkomponente der Grundschwingung und der zweiten Harmonischen näherungsweise berechnet werden kann. Die benötigten Anteile der Feldstärken können damit aus den Differenzströmen ermittelt werden.Das vorgeschlagene Verfahren wurde auf einer industriell gefertigten Schutzkarte implementiert. Die Überprüfung des Verfahrens erfolgte mit Berechnungsverfahren und durch Messungen im Labor.

     

Miscibility in poly-p-phenylene terephthalamide/nylon 6 and nylon 66 molecular composites

Miscibility and crystallization of poly-p-phenylene terephthalamide (PPTA)/nylon 6 and nylon 66 composites prepared by coagulation of isotropic ternary sulfuric acid solutions were studied. The apparent crystallinity of nylon 6 and nylon 66 in molecular composites was investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The solvation of nylon 6 crystals in PPTA matrix was observed when the PPTA content exceeds 70 wt%. Cross-hydrogen bonding seems to be responsible for the virtual disappearance of nylon 6 crystals. Specific interaction between PPTA and nylon 6 macromolecules and phase separation during thermal treatment has been discussed.