Spinning Disc Reactor for Green Processing and Synthesis - Process Intensification for Green Chemistry - page 72

0.1

Q=1ml/s
Q=3ml/s
Q=5ml/s
RSR (Q=94.4 ml/s) [33]
RPB (Q=9.5 ml/s, inlet radius=1 cm) [32]
RPB (Q=9.5 ml/s; inlet radius=5 cm) [32]
RPB (Q=5.6 ml/s, inlet radius=5 cm)[31]

[H+]=0.1 M
Water system

0.09

0.08

0.07

0.06

0.05

0.04

0.03

0.02

0.01

0

0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600

Rotational Speed (rpm)

Figure 3.14 Micromixing efficiency comparison between a 10 cm diameter SDR and other
intensified continuous reactor configurations. Reproduced from [ref 29] by permission of
John Wiley & Sons. 2012.

#

configurations such as large STRs. This feature is particularly advantageous for processes
involving:

(1) Heat-sensitive materials such as food products; for example, the pasteurization of ice
cream [35] and fruit juice [36] processing.
(2) Polymers where processing at high temperatures frequently leads to hot spots and
polymer degradation.
(3) Competitive reaction schemes in which exceedingly high residence time can signifi-
cantly reduce selectivity of the desired product if the product molecule can further
react to give unwanted byproducts [37].

Often, in continuous reactor configurations such as the continuously stirred tank reactor
(CSTR) and the microreactor, the flow rate is the main operating variable by which to
manipulate the residence time. In contrast, the SDR has an additional degree of freedom in
the disc rotational speed parameter, which can be controlled independently of the process
liquid flow rate to achieve the desired residence time without affecting the throughput.
In a recent comprehensive investigation [38], the residence time distribution (RTD) of
the thin liquid film was characterized as being close to the ideal plug flow regime, giving
each molecule practically the same processing experience on the rotating disc. This is an
important consideration in achieving, for example, narrow crystal or particle distributions
[7,39] and tight molecular weight distributions (MWDs) in polymerization processes
[40,41], as well as high selectivity in competitive organic chemical reactions [37]. It
has been demonstrated that near plug-flow conditions are generally attained at higher
disc speeds, higher liquid flow rates and lower liquid viscosities [38], as illustrated in