X-Ray Computer Tomograhy - Potential and Limitation for the Measurement of Local Solids Distribution in Circulating Fluidized Beds - Wirth, Karl-Ernst; Graßler, Thomas (1st World Congress on Industrial Process Tomography, 1999)
The characterization of the gas-solids flow inside a circulating fluidized bed, especially the knowledge about the solids distribution in the vertical tubes, is the basis for a optimum reactor design as well as for finding suitable operating con- ditions and for modeling the multiphase flow inside the reactor. To determine data of solids concentration with high spatial resolution an x-ray computer tomography system is used. This system mainly consists of a 60 keV x-ray source and an x-ray linear detector with 1024 sensitive elements, which gives 8 bit-values representing integral solids concentrations between the x-ray source and the detector. A number of experiments have been carried out both at the upflow and at the downflow of two different circulating fluidized beds containing glass beads of 70 μm at superficial gas velocities from 2 to 7 m/s. Results show that the x-ray computer tomography system is applicable to average solids concentrations from 1 up to 20 Vol-% of solids concentration in a tube with 0.19 m inner diameter.
UnivIS-Import:2015-04-16:Pub.1999.tech.ITC.mechve.xrayco_94
Keywords: X-ray; Computer tomography; Circulating fluidized bed; Multiphase flow

X-Ray Computer Tomograhy - Potential and Limitation for the Measurement of Local Solids Distribution in Circulating Fluidized Beds - Wirth, Karl-Ernst; Graßler, Thomas (Chemical Engineering Journal, 2000)
The characterization of the gas–solids flow inside a circulating fluidized bed, especially the knowledge about the solids distribution in the vertical tubes, is the basis for a optimum reactor design as well as for finding suitable operating conditions and for modeling the multiphase flow inside the reactor. To determine data of solids concentration with high spatial resolution an X-ray computer tomography system is used. This system mainly consists of a 60 keV X-ray source and an X-ray linear detector with 1024 sensitive elements, which gives eight bit-values representing integral solids concentrations between the X-ray source and the detector. A number of experiments have been carried out both at the upflow and at the downflow of two different circulating fluidized beds containing glass beads of 70 μm at superficial gas velocities from 2 to 7 m/s. Results show that the X-ray computer tomography system is applicable to average solids concentrations from 1 up to 20 vol% of solids concentration in a tube with 0.19 m inner diameter.
UnivIS-Import:2015-03-09:Pub.2000.tech.ITC.mechve.xrayco
Keywords: X-ray; Computer tomography; Circulating fluidized bed; Multiphase flow

You get what you screen for: a benchmark analysis of leaf branch compost cutinase variants for polyethylene terephthalate (PET) degradation - Fritzsche, Stefanie; Tischer, Florentin; Peukert, Wolfgang; Castiglione, Kathrin (Reaction Chemistry & Engineering, 2023)
Enzymatic recycling of polyethylene terephthalate (PET) is an innovative and environmentally friendly way to promote a circular plastics economy and reduce the use of petroleum-based plastic monomers. Despite, or rather because of the large number of natural and engineered enzymes discovered in recent years, there are substantial difficulties in comparing PET degradation rates between studies. The present study therefore gathered knowledge about potential pitfalls and the question of how benchmarking for enzymatic PET degradation should be performed. Since there is no progress to establish a well-defined standard substrate as well as uniform reaction conditions for comparative studies of PET hydrolases, we propose to carry a well-characterized enzyme as a reference in all studies. In this way, variants of the leaf branch compost cutinase (LCC) were benchmarked in miniaturized stirred tank reactors. Different mutants with amino acid exchanges inspired by natural or engineered PET hydrolases were compared. The best enzyme resulted from a combination of mutations contained in the ICCG variant of the LCC and the so-called DuraPETase. The product release rate of the resulting variant ICCG(DAQI) was 27% higher than the reference enzyme ICCG. Although the relative performance of the different enzymes seemed to be independent of the PET material used (bottles, textile fibres), the absolute degradation rates were strongly influenced by the substrate properties. In particular, compared to bottle PET, post-industrial textile fibres were efficiently degraded releasing 40 mg terephthalic acid per hour and mg(enzyme), resulting in complete degradation within less than 24 hours.
CRIS-Team WoS Importer:2023-06-02

Zeolite-Coated Porous Arrays: A Novel Strategy for Enzyme Encapsulation - Marthala, Venkata; Friedrich, Mona; Zhou, Zhou; Distaso, Monica; Reuß, Stephanie; Al-Thabaiti, Shaeel A.; Peukert, Wolfgang; Schwieger, Wilhelm; Hartmann, Martin (Advanced Functional Materials, 2015)
Zeolite Beta-coated stainless steel supports with gradient porosity are employed as filter-panels for lipase encapsulation. Enzyme encapsulation on the stainless steel porous discs is achieved via vacuum infiltration. Subsequently, two lipase-encapsulated zeolite Beta-coated stainless steel discs are attached using an adhesive. The zeolite Beta layer on the stainless steel discs largely prevents lipase leaching in comparison to the stainless steel discs without a zeolite layer. The activity of the lipase-encapsulated, attached zeolite Beta-coated stainless steel porous discs depends on the thickness of the zeolite Beta layer. It is shown that the biocatalytic performance of the lipase-encapsulated, attached zeolite Beta-coated stainless steel supports with a zeolite Beta layer thickness of ≈0.7–1 μm is better than the lipase-encapsulated, attached zeolite Beta-coated stainless steel supports with a zeolite Beta layer thickness of ≈2–3 μm in the lipase-catalyzed transesterification of vinyl propionate with 1-butanol using n-hexane as solvent.

Zerstäubung überhitzter Suspensionen mit unterschiedlichen Feststoffen und Feststoffkonzentrationen - Wirth, Karl-Ernst; Wellner, Sabine (-, 2001)
Ziel des Forschungsprojekts ist die Erzeugung eines feinstteiligen Sprays bei der Zerstäubung von Suspensionen. Mittels Suspensionssprays werden Oberflächen beschichtet sowie agglomeratfreie trockene Partikel hergestellt. Die Erzeugung feiner Suspensionströpfchen basiert auf dem Prinzip der Zerstäubung von überhitzten Flüssigkeiten. Hierbei wird die Suspension in einem Druckbehälter auf eine Temperatur erhitzt, die oberhalb ihrer Verdampfungstemperatur bei Umgebungsdruck liegt. Wird die Suspension schließlich mittels einer Einstoffdüse auf Umgebungsdruck entspannt, so kommt es zum Aufreißen des Freistrahls und zur Bildung des Suspensionssprays. Im Zentrum der Untersuchung steht der Einfluss des Überhitzungsgrades und der Düsengeometrie auf die Größe der Suspensionstropfen sowie den Strömungszustand im Spray. Darüber hinaus wird der Einfluss der Feststoffpartikel auf das Zerstäubungsergebnis untersucht. Es kommt dabei das optische Messsystem der Particle Image Velocimetry (PIV) zum Einsatz. Die Tropfengröße wird mittels Laserbeugung ermittelt
UnivIS-Import:2015-04-16:Pub.2001.tech.ITC.mechve.zerstu
Keywords: Überkritisches Fluid; Spray; PIV

Zinc oxide scaffolds on MgO nanocubes - Stankic, Slavica; Sternig, Andreas; Finocchi, Fabio; Bernardi, Johannes; Diwald, Oliver (Nanotechnology, 2010)
Powders of isolated and well-dispersed oxide nanocubes are promising components for photoelectronic applications that benefit from tunable optical properties, surface reactivity and the ease of realization of their controlled assembly. Here, we demonstrate that combustion of zinc and magnesium metal vapors at reduced pressures followed by subsequent vacuum annealing of the resulting nanoparticle powders yields single-crystalline ZnxMg1 - xO nanocubes of exceptional regular cubic shape and edge lengths below 25 nm. In line with ab initio calculations, which predict preferential Zn2 + segregation into low coordinated surface elements of the MgO nanocubes, we track the occupation of edge sites by chains of Zn2 + –O2 - units through their spectroscopic signatures. As a method to generate composite nanostructures with controlled spatial distribution of the chemical components, the annealing induced ion segregation can be extended to other well-dispersed metastable nanoparticles. We expect that the energy of segregation mainly depends on the site coordination number, which can promote controlled demixing within the nanoparticles
EAM Import::2019-03-12

Zirkulierende Wirbelschichten - Strömungsmechanische Grundlagen, Anwendung in der Feuerungstechnik - Wirth, Karl-Ernst (Springer, 1990)
Obwohl zirkulierende Wirbelschichten seit 50 Jahren großtechnisch zum Einsatz kommen, steht die wissenschaftliche Durchdringung dieses Verfahrensprinzips erst am Anfang. Bisherige Anwendungen der zirkulierenden Wirbelschicht waren im wesentlichen auf Verfahren mit einem festen Betriebspunkt beschränkt. Erst die Verwendung als Feuerungssystem mit der Forderung nach Teillastfahrweise offenbarte das mangelnde Wissen über die Strömungsvorgänge in zirkulierenden Wirbelschichten. Das vorliegende Buch soll dazu beitragen, diese Wissenslücke zu schließen. Die strömungsmechanischen Grundlagen der zirkulierenden Wirbelschicht wurden vom Autor erarbeitet, und er stellt sie hier erstmals dar. Dabei wird insbesondere gezeigt, welche Auswirkungen die Bauart der zirkulierenden Wirbelschicht auf deren Betriebsweise hat. Hierzu werden dimensionslose Zustandsdiagramme mitgeteilt. Im zweiten Teil des Buches wird ein einfaches Modell der zirkulierenden Wirbelschichtfeuerung erstellt, mit dessen Hilfe wärmetechnische Zustandsdiagramme berechnet werden können. In Verbindung mit den aus den strömungsmechanischen Grundlagen erhaltenen Zustandsdiagrammen können zirkulierende Wirbelschichtfeuerungen ausgelegt und deren Betriebsverhalten analysiert werden.
UnivIS-Import:2015-04-02:Pub.1990.tech.ITC.mechve.zirkul
Keywords: wirbelschicht; zirkulierend

ZnO superstructures via oriented aggregation initiated in a block copolymer melt - Klaumünzer, Martin; Distaso, Monica; Hübner, Jakob; Mackovic, Mirza; Spiecker, Erdmann; Kryschi, Carola; Peukert, Wolfgang (Crystengcomm, 2014)
A fast and simple one pot synthesis of ZnO nano- and microparticles initiated and driven by an amino block copolymer O,O′-bis(2-aminopropyl) polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol (Jeffamine®) is reported. The specific building mechanism of ZnO mesocrystals is investigated in detail using electron microscopy and diffraction methods. Mesocrystals with a complex superstructure are formed as a result of a consecutive and oriented multiple stage aggregation process: first a 0D → 1D aggregation process is observed, then a 1D → 3D aggregation process occurs in which secondary particles form cones and multiple cone symmetries. Dots, rods, cones, and multiple cones have been isolated within a time resolved study which clearly supports the growth model. To control the morphology of the product particles, the influence of relevant synthesis parameters including stirring and sonication of the intermediate were investigated. Extensive surface characterization of the resulting mesocrystals is presented using infrared and photoluminescence spectroscopies as well as thermogravimetric analysis. Even after multiple washing steps, the particles exhibit a Jeffamine® coated surface that allows for easy dispersion in both polar and nonpolar solvents. The obtained mesocrystals efficiently scatter in the whole range of visible light. © 2014 The Royal Society of Chemistry.

Unconventional optical Tamm states in metal-terminated three-dimensional photonic crystals - Korovin, Alexander V.; Romanov, Sergei G. (Physical Review B, 2016)
Unconventional optical Tamm surface states have been demonstrated in transmission and reflectance spectra of three-dimensional opal photonic crystals coated by thin metal films. These states appear in registry with diffraction resonances and localize the electromagnetic energy in asymmetric resonators formed by stacks of lattice planes and metal semishells. Tamm defect states provide the bypass for light at the edges of the Bragg diffraction resonances and thus reduce the diffraction efficiency. Despite the hidden nature of this effect, its magnitude is comparable to the extraordinary transmission associated with the surface-plasmon polaritons that are simultaneously excited at the surfaces of the corrugated metal films.
EAM Import::2019-03-12