Production process for diesel fuel components poly(oxymethylene) dimethyl ethers from methane-based products by hierarchical optimization with varying model depth

Poly(oxymethylene) dimethyl ethers (OMEs) are attractive components for tailoring diesel fuels. They belong to the group of oxygenates that reduce soot formation in the combustion when added to diesel fuels and can be produced on a large scale from methane-based products. This opens a new route for gas-to-liquid technology. The present work deals with a particularly favorable route for the large scale production in which OMEs are formed from methylal and trioxane. An OME process based on these educts is designed using two process models of varying depth. In a hierarchical optimization, in which the optimum obtained with a reduced model is used as a starting point for the optimization with the detailed model, an optimal design is found. The resulting design is further adopted to practical needs including a possibility of side-product purge. This work shows that OME production from methylal and trioxane is feasible with technology that could be used in very large scales. The physical property model that is required for the design of the OME process is described in the present work. It is based on literature data on thermo-physical properties and reaction data from previous work of our group. That database is complemented in the present work by measurements of the density of pure OMEs and the vapor–liquid equilibrium in the system (dioxymethylene dimethyl ether + trioxane).     

Eddy currents and electrical surface charges

In eddy current calculations, the displacement current in the non‐conducting space surrounding the eddy current region is usually neglected. This assumption enforces that the electric charge density and the accompanying normal components of the eddy current density on the surface of the eddy current region must vanish. If the field exiting source currents are not accompanied by charges this assumption may yield acceptable results for the eddy current distribution. However, if the field exiting source currents are accompanied by charges, this assumption may lead to totally wrong results for the current distribution in the eddy current region. An example is given which makes plain this point. To obtain correct results it is not necessary to employ the full set of Maxwell's equations capable to describe wave propagation phenomena also outside the eddy current region. It is shown in the paper that by replacing the displacement current density in the field describing equations by a specifically chosen current density function makes it possible to determine eddy currents and surface charges within the quasi‐stationary calculation scheme for arbitrary field exciting source currents which may or may not be accompanied by charges. The solution obtained in this way is shown to be unique. Copyright © 2003 John Wiley & Sons, Ltd.     

Einsatz physikalischer Analysemethoden zur Charakterisierung von dünnen Schichten und Grenzflächen in der Halbleiterindustrie

Characterization of thin films and interfaces are necessary in semiconductor industry to ensure high yields and the required reliability of the products. Requirements to thin film and interface analysis are reviewed, and typical applications in semiconductor industry are shown. Thin film characteristics which have to be determined using physical analysis techniques are film geometry, surface and interface roughness, chemical composition, and microstructure. Advances in physical failure analysis are essential to the reduction of feature size and introduction of advanced materials and processes for future technology generations. Future trends are discussed. To reduce the time for problem solving in the manufacturing process, out of‐fab characterization tools will partly move to“at‐line” labs which are located next to or sometimes inside the cleanroom.     

Interfacial tension in systems with a supercritical component at high pressures

Interfacial tension of the binary systems pelargonic acid/ethane, pelargonic acid/carbon dioxide, linoleic acid/ethane, and linoleic acid/carbon dioxide was measured at 313, 333, and 353 K and pressures ranging up to 250 bar, using the capillary rise and Du Nouy ring methods. Both these methods yield similar values. The surface excess of supercritical components is deduced from the measurement results with the aid of Gibbs adsorption equation. The surface excess concentration increases with increasing gas activity, runs through a pronounced maximum, later decreasing rapidly to very small values. Near the surface excess maximum, a falling film of fatty acids disintegrates into a mist of tiny droplets.     

Die Mikroflora des Sauerteiges

Zusammenfassung Es wurde dem Verhalten heterofermentativer Sauerteigbakterien bei gemeinsamer Kultur mit Hefen nachgegangen. Diese Untersuchungen erstreckten sich aufLactobacillus brevis, L. brevis var. lindneri undL. fermentum einerseits, sowic aus Sauerteigen isolierte Hefen (Candida krusei, Pichia saitoi, Torulopsis holmii, Saccharomyces cerevisiae) andererseits. Das Verhalten der Mischkulturen wurde an Sauerteigen aus Roggenmehl (Type 997, Teigausbeute 180, 27–28 °C, 18 Std) studiert. Je nach den zueinander in Wechselbezichung tretenden Sauerteigbakterien und Hefen ergab sich eine unterschiedliche Beeinflussung der Säurebildung. WährendTorulopsis holmii insbesondere die vonLactobacillus brevis undL. brevis var. lindneri ausgehende Teigsäuerung um bis zu fünf Einheiten erhöhte, bedingteSaccharomyces cerevisiae eine Förderung der vonL. brevis var. lindneri undL. fermentum ausgehenden Säuerung des Sauerteiges.

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The microflora of sourdoughXV. Communication: On the behaviour of heterofermentative sourdough bacteria and yeasts in mixed culture

Summary The behaviour of heterofermentative sourdough bacteria in mixed culture with yeasts was investigated. The investigations includedLactobacillus brevis, L. brevis var. lindneri andL. fermentum as well as several yeasts, isolated from sourdough (Candida krusei, Pichia saitoi, Torulopsis holmii, Saccharomyces cerevisiae). The behaviour of the mixed cultures was studied in ryeflour doughs (Type 997, dough yield 180, 27–28 °C; 18 h). Depending on specific interrelationships between types of sourdough bacteria and yeasts influence on acidification varied.Torulopsis holmii raised the dough acidification produced byLactobacillus brevis andL. brevis var. lindneri by up to five units;Saccharomyces cerevisiae enhanced the acidification byL. brevis var. lindneri andL. fermentum.

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Nr. 4676 der Veröffentlichungen der Bundesforschungsanstalt für Getreide- und Kartoffelverarbeitung, Detmold

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Diese Untersuchungen wurden ermöglicht durch eine finanzielle Förderung seitens des Bundesministeriums für Forschung und Technologie im Rahmen des Programms Biologic and Technologic     

Simulation of biological degradation of aromatic amines in river bed sediments

Testfilter experiments are reported for river Elbe water spiked with aromatic amines in order to determine biodegradation rates. For river Elbe water the mean degradation rate of DOC (C0 = 6.64 mg l-1) was 26.7 +/- 8.8% after 6.8 days. No significant effect on the DOC degradation rate was observed with the addition of aromatic amines. Large differences in the biodegradation behaviour of the aromatic amines were observed: aniline was eliminated within 3 h, whereas the degradation of 2-nitroaniline was only 40% after 14 h effective contact time. Degradation curves were mostly of a simple logarithmic type, demonstrating first-order kinetics. The degradation rate of 2,4,6-trichloraniline increased by a factor of 20 within 6 weeks due to the adaptation of the testfilter biofilm. A linear relationship between available pKa-values and the logarithm of the experimental degradation rates was found. Thus, the results of the testfilter experiments may be extended to the estimation of the biodegradability of non-tested aromatic amines.