Showing papers by "DECHEMA published in 1987"

Exhaust gas purification using immobilised monocultures (biocatalysts)

Abstract: The paper is concerned with the purification of exhaust gases using biocatalysts in a trickle bed reactor. Substance specific strains (monocultures) which were, for example, immobilised on activated carbon served as biocatalyst. Technically important solvents and substances such as aldehydes, methyl ethyl ketone and ethyl acetate were used as pollutants. Their concentration was about 5–40 ppm in the exhaust gas to be purified. The experiments show that with suitable bacterial, strains space velocities of about k *=1500 h-1 can be obtained at a conversion of 90%. The mass transfer through the liquid film around the activated carbon grains seems to be rate determining.

Transition from oxidation to sulfidation of Fe-Cr alloys in gases with low oxygen and high sulfur pressures

Abstract: Fe-Cr alloys with 17–30% Cr show in H2-H2O-H2S mixtures at 1273 and 1073 K a transition from protective oxide scale formation to rapid sulfidation. The critical oxygen pressure to stabilize the oxide formation increases with increasing sulfur pressure of the gas and decreasing Cr content of the alloy. Cr2O3 with traces of Fe2O3 is formed under these conditions. Below the critical oxygen pressure, a primarily formed Cr2O3 film becomes overgrown by (Fe, Cr)S. The kinetic boundary of oxidation-sulfidation, which lies in the stability field (Fe, Cr)S + spinel Fe1+xCr2−xO4 of the Fe-Cr-O-S phase diagram, is explained with the help of the Fe-Cr-O-S phase diagram and the assumption that Fe diffuses faster through the (Cr, Fe)2O3 solid solution than does Cr.

Microdissection and microcloning of the long arm of human chromosome 7.

Abstract: DNA-fragments from the region of the long arm of human chromosme 7 to which the CF-locus has been mapped recently were isolated by microdissection and microcloning. We developed a new fixation procedure resulting in inserts of 1.0–7.0 kb in length with a mean value of 2.9 kb. Regional mapping of three clones on 7q was carried out by the use of different hybrid cell lines containing fragments of human chromosome 7.

Cystic fibrosis: typing 48 German families with linked DNA probes.

Abstract: Two hundred and thirty five subjects from 48 German cystic fibrosis (CF) families were typed for restriction fragment length polymorphisms (RFLPs) detected by the probes pmet H, pmet D, and pJ 3.11, known to be tightly linked to the CF gene. Gene and haplotype frequencies suggest a linkage disequilibrium with the CF locus. The analysis of the predictive value of this typing in individual CF families indicates that the combined use of these probes provides a powerful diagnostic system both for carrier detection and prenatal diagnosis. In 33 out of 48 families carriers and non-carriers could be identified, and in 26 of these 33 families prenatal diagnosis could discriminate between affected and unaffected offspring.

Computer simulation of oxide scale cracking/healing processes under substrate creep at high temperatures and comparison of the results to experimental data

Abstract: A computer programme is described which simulates the cracking and healing processes in protective oxide scales on heat-resistant alloys under tensile straining at high temperatures. The main aim of the programme has been to calculate the critical strain rates for the maintenance of the protective effect of oxide scales after cracking by healing. The results from simulation calculations using input data for 3 heat-resistant steels investigated earlier are compared to experimental results for these materials. The comparison reveals good agreement between calculated and experimental data concerning the critical strain rates for the maintenance of the protective effect by crack healing. The programme, thus, offers a tool for the theoretical estimation of critical strain rates when knowing some necessary mechanical data of the scale and the oxidation rate constant. Computersimulierung der Risbildung und -ausheilung in Oxidzunderschichten wahrend des Hochtemperaturkriechens von Metallen, unter Vergleich mit experimentellen Ergebnissen Es wird ein Rechnerprogramm beschrieben, das die in schutzenden Oxidschichten auf hitzebestandigen Legierungen unter Zugverformung bei hohen Temperaturen ablaufenden Risbildungs- und Ausheilvorgange simuliert. Das Hauptziel des Programms ist es, die kritischen Dehngeschwindigkeiten bezuglich des Erhalts der Schutzwirkung der Deckschichten nach Risbildung uber Ausheilvorgange zu berechnen. Die Ergebnisse von Simulationsrechnungen, bei denen Eingabedaten von 3 bereits fruher untersuchten hitzebestandigen Stahlen verwendet wurden, werden mit experimentellen Ergebnissen dieser Werkstoffe verglichen. Der Vergleich weist eine gute Ubereinstimmung zwischen berechneten und experimentellen Werten der kritischen Dehngeschwindigkeiten fur den Erhalt der Schutzwirkung nach Risbildung uber Risheilung auf. Das Rechnerprogramm bietet somit die Moglichkeit, kritische Dehngeschwindigkeiten theoretisch abzuschatzen, wenn einige notwendige mechanische Kennwerte der Oxidschicht und die parabolische Oxidwachstumskonstante bekannt sind.

Investigations on the Interaction of LCF and Oxidation

Abstract: In LCF-tests the behaviour of protective oxide scales and the first stages of materials damage in the subsurface zone after oxide scale cracking have been investigated. The tests have been performed with Ni 99.2 and Alloy 800 at 300°C and with a 9.5 Cr-steel at 650°C. Concerning oxide scale cracking tensile periods in LCF-deformation are more critical than compressive periods. The strains to scale damage are given in the paper. For Alloy 800 it has been found that the time of preoxidation decides on the beginning of surface crack initiation in the metal. This could be referred to the change of the Cr-content in the subsurface zone due to oxide scale formation and to subsequent Cr-rediffusion from the bulk material. The Cr-content in the subsurface zone decides on whether a protective chromia or a non-protective Fe-rich scale is formed during scale crack healing. For the 9.5 Cr-steel preoxidation and LCF-deformation lead to marked Cr-depletion in the subsurface zone and by this to the formation of non-protective Fe-rich oxide during scale crack healing.

Entwicklungstrends von Sensoren in der chemischen Technik

Abstract: Trends in the development of sensors in chemical engineering. The present article surveys the state of the art and future developments of sensors, mainly in the chemical industry. Existing requirements are compared with solutions becoming possible by means of present or developing new technologies and measuring concepts. The discussion covers a wide range, from sensors for classical state variables to sensors for the determination of concentrations and biotechnological variables. It includes data communication and modern process control. Among new technologies microelectronics and integrated microcomputers are rated highest; in addition possible uses of electrooptics and glass fiber techniques are mentioned as well as solid state and biochemical components. Within the new concepts, measurements based on modelling and multisensor systems have gained a firm position in practical applications.

Process and device for the removal of so2 from gases containing so2

Abstract: of EP01261701. Process for the removal of SO2 from SO2 -laden gases, distinguished by the fact that a multichamber cell consisting of several sub-chambers connected with one another by diaphragms is used, in which a portion of the SO2 oxidizes in one sub-chamber in the presence of an aqueous medium, air and/or oxygen and of copper oxide and/or metallic copper, with the formation of copper sulphate, which dissolves in the aqueous media, and is thus removed from the gas flow and in a further sub-chamber containing electrically conductive packing and/or electrode internals a further portion of the SO2 is contacted with an electrolytically conductive scrubbing fluid and the SO2 electrochemically removed from the gas flow to be cleaned by means of anodic oxidation after absorption, the dissolved copper formed in SO2 removal being reduced to metallic copper on electrically conductive packing and/or electrode internals as a cathodic counterreaction in a further chamber of the multi-chamber cell.

The Limits to the Protective Effect of Oxide Scales on High Temperature Materials Which are Subjected to Strains

Abstract: The integrity of dense protective oxide scales on high temperature materials is a prerequisite for the resistance of these materials to corrosive environments. Under service conditions stresses and strains arise in high temperature structural components which are transferred into the oxide scales. The protective scales may crack under these conditions and the damage initiated by the interaction of corrosion and mechanical loading may lead to premature failure of the structure.