Page 190 - Design of Simple and Robust Process Plants
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5.5 Intensification of Process Functions 175
A rotating machine was developed as the heart of an absorption heat pump by
Ramshaw and Winnington (1997) at ICI, and-later at the University of Newcastle
and at Interotex Lim. The development focuses on a double-effect absorption heat
pump and is intended for use in small-scale air-conditioning and refrigeration
plants. Field tests of this equipment are currently under way.
Rotational particle separators for dust and mist streams of particle sizes >0.1 lm
have been described by Brouwers (1996). The core component of the rotational parti-
cle separator is the filter element, which consists of a multitude of small axial chan-
nels rotating around a common rotational axis. The gas streams flow axially through
these channels, where the particles are centrifuged against the wall. The gases leave
the channels, while the particles are collected at the walls where they are periodically
removed at high velocities.
Reactive stripping in a rotating packed bed has been used in the production of
hypochlorous acid at Dow Chemical (Trent et al., 1999). This problem was recog-
nized as an opportunity to utilize centrifugal techniques by virtue that although the
reaction employed:
NaOH + Cl 2 ® HOCl + NaCl
had rapid kinetics, the HOCl produced was subject to undesirable decomposition to
chlorate. The key to the development of the process was the rapid transfer through
the maximum decomposition pH zone, which maximized stripping of the HOCl to
the vapor phase. The solution to the problem was found in a rotating packed bed
which moved liquid through a porous packing while the gas moved countercur-
rently. This resulted in an industrial application with the design principle of a rotat-
ing packed bed that could be applied to different separations, including gas/liquid
or gas/liquid/solid, absorption, and adsorption (Figure 5.27).
Liquid outlet
Gas out let
Liquid Driver
inlet
Seal
Packed bed
Gas flow
Liquid flow
Gas inlet
Fig. 5.27. Rotating Packed bed applicable for fast; G/L and F/L/
S reactions, absorption, adsorption.