DECHEMA

About: DECHEMA is a nonprofit organization based out in Frankfurt am Main, Germany. It is known for research contribution in the topics: Corrosion & Oxide. The organization has 756 authors who have published 1307 publications receiving 25693 citations.

Improvements in the thermodynamic and kinetic considerations on the coating design for diffusion coatings formed via pack cementation

Abstract: An enhanced coating design model for the pack cementation process was applied in order to acquire the appropriate process parameters, which lead to the formation of optimized aluminide coatings. This coating design model was derived from former considerations, which were based on austenitic AISI 321 steel. Due to further developments in the thermodynamic and kinetic approach of the underlying model, which include the incorporation of thermodynamic calculations for the considered Fe-Al and Ni-Al intermetallic systems and a new analysis method of their diffusion properties, the Al activities within the intermetallic phases, the pre-factor of the diffusion coefficient D0 and the activation energy EA can be determined. Based on new considerations, the coating design model is a self-sufficient system, in which the thermodynamic and kinetic values determined showed good agreement with literature values.

Ion exchange cell for continuous electrochemical treatment with two modified ion exchange electrodes separated by an ion exchange membrane useful for removal of ions from aqueous and organic solutions, and especially for water softening

Abstract: Ion exchange cell for continuous electrochemical water treatment with at least two modified ion exchange electrodes separated by an ion exchange membrane, which can be regenerated by altering the polarization is new. An Independent claim is included for a process for treating water (water softening) in which the cell is electrochemically conditioned, brought into contact with an ion containing solution, and finally the ion laden membrane (sic) is regenerated by application of a counter-voltage.

Modelling of the vented methanol/acetic anhydride runaway reaction using SAFIRE

Abstract: Venting experiments were carried out during thermal runaway chemical reactions to evaluate the predictive performance of the coupled thermodynamic fluid-dynamic and the reaction kinetic parts of the SAFIRE code. The exothermic esterification of acetic anhydride and methanol served as the model reaction. Overall, with SAFIRE it is possible to qualitatively predict the transient reactor pressure during venting of a runaway reaction. It is possible to reproduce the influence of a variation in initial vessel liquid level or cross-sectional area of the discharge line on the transient pressure. The calculated reactor pressure profile deviates in terms of absolute values from the measured profile, indicating that the computer code needs to be further extended by introducing improved physical models.

Process for separating gaseous organic noxious material, even present as traces from exhaust gases, by biological oxidation using bacteria

Abstract: 1. A process for eliminating gaseous organic pollutants, which can also be present in traces, from waste gases by biological oxidation using bacteria, wherein the gas stream containing one or more organic pollutants is led through one or more biologically active layers in fluidized bed reactors and, for wetting the bacterial cultures fixed on the surface of the carrier, a liquid stream is circulated in a co-current or counter-current during operation, characterised in that the biologically active layers are produced by bringing a porous, pollutant-adsorbing, carrier material, which has a high internal surface area and is selected from the group comprising activated carbon, zeolite and silica gel, into contact with a pollutant-specific suspension of a bacterial monoculture and/or mixed culture.

Damage of a heat‐treatment retort by metal dusting attack

Abstract: The damage of a heat-treatment retort which was made of cast Fe36Ni21Cr steel and used under a carburizing atmosphere at about 900 °C has been investigated. Strong corrosion attack had occurred, leading locally to pitting on the surface or even to hole formation in the retort walls. An oxide layer rich in chromium had formed on the outside of the metal followed by a precipitation zone of carbides. These carbides decomposed near the surface into graphite and the corresponding metal, similar to “metal dusting”. The strong corrosion attack was often correlated with preexisting imperfections in the cast material like shrinkage cavites or microporosity. Schaden an einer Warmebehandlungsretorte durch Metal Dusting Angriff Ein Schadensfall an einer aus Fe36Ni21Cr im Schleudergusverfahren hergestellten Warmebehandlungsretorte wurde untersucht. Die Retorte wurde unter aufkohlender Atmosphare bei etwa 900 °C betrieben und zeigte einen starken lokalen Korrosionsangriff in Form von Grubchenbildung bis hin zu Lochbildung. Die Untersuchungen zeigten, das sich an der Oberflache eine chromreiche Oxidschicht ausgebildet hat. In der darunter liegenden Metallrandzone fand eine starke innere Karbidbildung durch Aufkohlung statt. Vergleichbar dem „metal dusting“-Prozes zerfallen die Karbide in der Nahe der Oberflache in Kohlenststoff und das entsprechende Metall. Der verstarkte Korrosionsangriff war haufig mit herstellungsbedingten Fehlern im Guswerkstuck wie Lunker und Mikroporositat verbunden.