New advances in agitation technology for exothermic reactions in very large reactors

CFD simulations of stirred-tank reactors for gas-liquid and gas-liquid-solid systems using OpenFOAM®

“…Investigations of the effects of reactor parameters and operating conditions such as the geometry of the tank, impeller type, size and location, impeller rotation speed and gas flow rate on the reactor characteristics including flow regimes and patterns, gas hold-up, power-consumption, mixing time and mass-transfer coefficient between the phases have been carried out for decades (Ford et al 2008;Joshi et al 2011a; Kumaresan and Joshi 2006;Miller 1974;Nienow et al 1985;Nienow 1998;Parasu-Veera, Patwardhan, and Joshi 2001;Rewatkar et al 1993;Sawant and Joshi 1979). For large-scale, tall-thin, industrial gas-liquid STRs, multiple impellers are usually preferred over a single impeller because multiple impellers can have better gas utilization due to the high residence time of gas bubbles, maintain homogeneity in the reactor, provide high surface-to-volume ratio and offer lower shear than single-impeller STRs for shear-sensitive systems (Ahmed et al 2010;Dutta and Pangarkar 1995;Himmelsbach et al 2006;Kasat and Pandit 2004;Khopkar et al 2006;Shewale and Pandit 2006;You et al 2014). However, the complexity of the flow in STRs with multiple impellers increases with increasing number of impellers as any change in the reactor parameters, such as tank aspect ratio, number, type, size, location and configuration of impellers and operating conditions, may influence the reactor operating characteristics significantly.…”

Solids distribution in tall tanks

“…The extensive work in solids–liquid systems is well represented in Atiemo‐Obeng et al (2004); Paul et al (2004), and more recent studies such as Bao et al (2005); Ditl and Rieger (2006); Himmelsbach et al (2006); Brown et al (2007); Khazam and Kresta (2008); Spogis and Nunhez (2009); and Guida et al (2010). These works involve experimentation and/or computer modelling to examine a variety of floating or settling solids, and traditional and/or new impeller types operating at various conditions of agitation speed and flow direction.…”

Prozessintensivierung in der Misch‐ und Reaktionstechnik

“…Exponenten über dem Durchmesserverhältnis auf [7,9,10]. Exponenten über dem Durchmesserverhältnis auf [7,9,10].…”

“…Radialförderer weisen einen geringfügig abweichenden Faktor vor bzw. Exponenten über dem Durchmesserverhältnis auf [7,9,10]. Damit ergeben sich unabhängig vom Rührertyp die Einflussgrößen auf die Mischzeit zu:…”

“…B. Scheiben-oder Schrägblattrührer würden bezüglich Mischzeit und Drehmomenten noch ungünstiger abschneiden[10]. Das kleine Durchmesserverhältnis erfüllt die Forderung nach hoher Drehzahl, um bei gleicher Leistung mit kleinem Drehmoment zu fahren.…”