Rotor stator reactor

High-intensity inline devices are often used to mix fluids in the process industries. Such devices include simple pipes, baffled pipes, tees, motionless mixers, dynamic mixers, centrifugal pumps, ejectors, and rotor/stator mixers. In addition to their traditional application in physical processes such as mixing and dispersion, such devices can provide very effective environments for mass transfer and chemical reaction to take place. Furthermore, combining effective inline mixing with heat transfer is the basis of combined heat exchanger reactors (HEX reactors). 

When a high degree of shear on small liquid volume is desired, a rotor-stator stirrer is used (see Fig. 4). This stirrer consists of a blade or paddle stirrer enclosed by a ring of baffles. This type of stirrer thus alleviates the need for separate baffles in the vessel. This stirrer is not useful for biological reactors, but finds special use in polymeric reactors containing non-Newtonian liquids. 

Figure 5.17 Disc stator-rotor disc reactor. Source Reproduced from Ref [49] 2014 with permission from Elsevier B. V.

Chen, L.-F., Chen, G.-Z. and Wang, J.-X. (2011) High-Throughput Microporous Tube-in-Tube Microreactor as Novel Gas-Liquid Contactor Mass Transfer Sta y. AIChE J., 57 (1), 239-249. Meeuwse, M., van der Schaaf, J., Kuster, B.F.M. et al. (2010) Gas-liquid mass transfer in a rotor-stator spinning disc reactor. Chem. Eng. ScL, 65 (1), 466-471. 

The Taylor-Couette reactor (see Chapter 5) is also a rotor stator mixer, but is discussed separately. Units such as the Marbond HEX-reactor demonstrate mixing plus reactions plus heat transfer in one unit, and these are also discussed in Chapter 5. 

The nonoriented steels are subdivided into low, intermediate, and high siUcon steels. The first contain about 0.5—1.5% siUcon, used mainly in rotors and stators of motors and generators. Steels containing ca 1% siUcon are used for reactors, relays, and small intermittent-duty transformers. 

Saturable reactors, which are adjustable by a small dc signal, have also been used for both primary (stator) and secondary (rotor) control. In the primary they control motor voltage and therefore torque. In combination with fixed secondary resistors and feedback from a tachometer, this system can be used for precise speed and torque control of cranes, hoists, etc. Even reversing can be accomplished by using two saturable reactors in each of two (of three) phases. Other combinations of fixed or saturable reac tors in the primaiy and/or secondaiy, all combined with secondary resistors, provide a wide range of capabiUties and flexibihty for the wound-rotor motor. 

Fluid viscosity and volume to be mixed are the most significant factors. Propellers viscosity <3000 mPa-s volumes <750 m Turbines and paddles viscosity <50,000 mPa-s volumes <75 m Liquid jets viscosity <1000 mPa s volumes >750 m Air agitation viscosity <1000 mPa-s volumes >750 mT Anchors viscosity <100,000 mPa-s Re <10,000 volumes <30 mT Kneaders viscosity 4,000 to 1.5 x 10 mPa s volumes 3 to 75 m Roll mills viscosity 10 to 200,000 mPa s volumes 60 to 450 m For viscosity >10 consider extruders, Banbury mixers, and kneaders. Paddle reel/stator-rotor gentle mechanical mixing for coagulation, viscosity <20 mPa s volumes large. Motionless mixers viscosity ratio <100,000 1 continuous and constant flow rates residence times <30 min and flow rate ratio of <100 1. Other related sections are size reduction (Sections 16.11.8.1 and 16.11.8.3), reactors (Section 16.11.6.10), and heat transfer (Section 16.11.3.5). 

Stator-rotor spinning disc reactor (Stator-rotor SDR)... 

Unfortunately, the available data are sparse at present. From the heat transfer point of view, the suitability of the reactors may be put in deceasing order as SSTR, stator-rotor SDR, HEX reactors, AFR, SDR, ACR/ATR, OBR and HIGEE. If the interphase transfer dictates the reaction rate, the volumetric mass-transfer coefficient plays a dominant role. The micro-mixing and residence time also are of importance in the case of fast reactions and thermally unstable products. The above ordering (but for the SDR) could be used for gas-liquid or liquid-liquid phases. If solid-liquid or solid-liquid-gas are involved, the decreasing order could be OBR, ACR/ATR, AFR, HIGEE, stator-rotor SDR, and SSTR. Studies are underway on the characteristics of the reactors. These would help to ascertain their relative merits quantitatively in the future. 

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