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if significant progress towards developing and implementing online monitoring tools in
challenging reactor environments such as miniaturized, low-volume processing systems is
to be achieved.
Mechanistic modelling of SDR processes is quite challenging due to the inherently
unstable nature of the films. Although some effort has been directed at developing models
for mass transfer [21], polymerization [69] and photocatalytic reations [70], there is clearly
great scope for further work in this area. In particular, more generally applied models
should be developed for heat- and mass-transfer and chemical-reaction systems.
3.5.2 Limited Process Throughputs
Limitations on flow rate in an SDR are imposed in order to achieve the benefits of thin-film
flow on a given disc size. Throughputs of 300 kg/hour on a 1m diameter disc may be more
than adequate for pharmaceutical and fine chemicals industries but they are not sufficient
for the bulk chemicals/petrochemicals industry, where annual throughputs of the order of
100 000 tonnes are the norm. To address this limitation, multi-disc designs operating in
parallel could allow high production capacities. Such systems have yet to be designed, built
and tested.
3.5.3 Cost and Availability of Equipment
SDRs are still relatively expensive compared to conventional, established technologies
such as stirred tank vessels. A small-scale reactor (10-15 cm diameter) complete with a
temperature-controlled bath and feed pumps has been known to cost more than £150 000.
More equipment manufacturers should be involved in developing this technology and
making off-the-shelf units more readily available to industry users. Costs can also be
expected to be significantly reduced if more reactors are supplied on the market.
3.5.4 Lack of Awareness of SDR Technology
There is a need for industrial chemists and development engineers to familiarize them-
selves with SDR and PI technologies in general and to be aware of the potential benefits of
such technologies for their specific applications. This should help them match the
capability of the technology in question with their process requirements and better select
reactors for a given process. Short courses on SDR principles and potentials should be
offered to people in industry across a wide range of sectors, in order to generate more
widespread awareness of the opportunities presented by this technology.
3.6 Conclusion
The SDR represents a step change in reactor technology development. It offers a
combination of highly desirable characteristics for a niche of applications involving
fast, highly exothermic reactions. Some of its characteristics, such as extremely short
and controllable residence times, are hard to replicate in any other technologies without
incurring severe penalties, rendering the SDR unique in some aspects. The SDR holds
much promise for highly efficient processing in many applications particularly relevant to
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