Continuous high-intensity mixing of two fluids for carrying out fast precipitation is an important method for producing nanoparticulate solids for diverse applications, e.g., in fine chemistry, pigment or catalyst preparation. Continuous precipitation with a newly developed micromixer technology, the so-called valve-assisted micromixer, allows for stable operation without clogging for several days. Scaleup to technically relevant scale was achieved without differences in the quality of the precipitate. The technology has been extensively tested for preparation of catalysts for production of carbon nanotubes.

Modulare Anlagen in der Verfahrenstechnik wie z. B. Containeranlagen bieten interessante Perspektiven im Vergleich zu etablierten Produktionsanlagen für chemische oder pharmazeutische Prozesse. Für das Konzept der modularen Chemieanlagen sehr gut geeignete modulare Mikro‐bzw. Millireaktoren befinden sich in der Phase der Einführung in den Markt der Prozesstechnologien. Entsprechend hoch ist die Bedeutung von Referenzbeispielen im Produktionsmaßstab. Die Technologieplattform Mikro‐/Millireaktionstechnik erfüllt die Anforderungsprofile von Containeranlagen, was für beispielhaft ausgewähltes Equipment demonstriert wird.

The gas-liquid flow behavior through a milli-scaled channel provided with a staggered herringbone-like static mixer was investigated using high-speed recordings. For three different substance systems consisting of water, 5 wt % acetic acid in aqueous solution, and propylene glycol as liquid phase and nitrogen as gas phase, flow patterns and their transitions were determined by analyzing image sequences of the flow and summarized in flow pattern maps. Surge flow, slug flow, and bubbly flow were observed at different flow rates. The flow distribution and transitions between flow patterns mainly depend on the viscosity and surface tension of the liquid phase. By just reducing the surface tension, slug flow is not observed, and thus an early transition into a bubbly flow regime takes place. An increase in viscosity counteracts this effect.

Der Wärmeübergangskoeffizient ist ein entscheidender Parameter hinsichtlich der Sicherheit bei der Durchführung exothermer Reaktionen im Produktionsmaßstab. Die prozessseitigen Wärmeübergangskoeffizienten in kleinskaligen rechteckigen Kanälen mit darin eingebauten statischen Mischeinlagen wurden experimentell bestimmt und ihre Abhängigkeit von der Strömungsgeschwindigkeit, der Geometrie und der Wärmeleitfähigkeit sowie vom Kanalquerschnitt wurde untersucht. Im Vergleich zum Leerkanal wird durch die Mischeinlagen eine deutliche Steigerung des Wärmeübergangs durch erzwungene Konvektion beobachtet.The heat transfer coefficient is a crucial parameter with regard to safety in the execution of exothermic reactions in production scale. The process-side heat transfer coefficients in small-scale rectangular channels equipped with various static mixing elements were determined experimentally and their dependence on flow rate of the process fluid, geometry and thermal conductivity as well as on the cross-section of the channel was investigated. In comparison to an empty channel, inserts of any kind lead to an increase of the heat transfer coefficient due to forced convection.

The mixing performance of a distributed-feed plate-type reactor equipped with curved channel design and microstructured multinozzle injectors was investigated. Almost ideal plug flow behavior with 300 < Bo < 2000 for Re numbers between 338 and 3610 and total flow up to 240 L/h was ascribed to bend-induced vortices in combination with modulated flow velocities along the flow path. The micromixing performance of multinozzle jet injectors which consisted of round nozzles with 100 and 140 μm diameters in a circular pattern was studied using a decolorization reaction and the Villermaux-Dushman reaction in conjunction with the IEM model. Mixing times as obtained by the first method were generally higher than that obtained by the second method but both were in the range of milliseconds. The dependence of respective mixing times on the energy dissipation rate was found to scale with power-law exponents of −0.58 and −0.43, respectively, and suggested engulfment as the limiting mixing mechanism.