Chemistry Reference
In-Depth Information
desired production rate. This concept has been demonstrated in a feasibility study
undertaken by SmithKline Beecham in the SDR [71], where a lab-scale reactor could
match the production capacity of a batch process giving 8 tonnes of product per annum.
Cutting down on the process development stages can avoid lengthy delays, as these stages
alone can take up to 3 years when scaling up batch processes, which is a considerable
amount of time in a product lifespan of 20-25 years before patent expiry.
1.5.2 Process
The process benefits of higher selectivity, faster reaction rates and better product properties
were explored in great detail under the various technologies considered in Section 1.4.
Safety in the chemical industry is one of the highest priorities for health-and-safety
regulatory bodies following a number of fatal incidents involving large inventories of
hazardous materials and exothermic runaways in batch reactors, such as the Bhopal
disaster in 1984 [72]. Adopting the PI approach can substantially improve the intrinsic
safety of a process as there will be a significantly reduced volume of potentially hazardous
chemical at any one time, in a smaller intensified unit. In addition, one of the objectives of
PI is to move away from batch processing to small continuous reactors, which have a more
efficient overall operation, especially in the case of hugely exothermic reactions, in which
the heat can be removed continuously as it is being released. It is to be borne in mind,
however, that when intensifying a process, for example by integrating process steps, the
process will be prone to becoming more complex, and overall safety considerations on the
basis of a number of parameters need to be properly assessed, as highlighted in a recent
study [73].
Another major advantage of PI technologies is that by virtue of their greatly improved heat
and mass transfer, they allow process conditions to be employed which would previously
have been impossible with conventional technologies. These are what Hessel refers to as the
'novel process windows' offered by PI [74]. Several applications, particularly related to
microreactors [74-76] and SDRs [77,78], in which these more intense operating conditions -
such as highly concentrated reaction systems, higher temperatures and higher pressures -
have been investigated, are documented in the literature.
1.5.3 Environment
PI technologies have tremendously appealing environmental implications, whereby a
small, compact, highly intensified plant is more likely to be below the tree line, making it
far less of an eyesore for the general public than the unsightly and massive steel works
characterizing our present chemical plants. Furthermore, novel reactor designs based on
the PI concept will enable clean technology to be practised by enabling waste minimization
at source. In other words, high-selectivity operation in intensified reactors will reduce or
eliminate altogether the formation of unwanted byproducts, which, if not removed from the
effluent before discharge, can cause irreversible damage to the environment. High-purity
product - which is hence of improved quality - will thus be obtained without incurring
enormous downstream purification costs.
The improved energy efficiency foreseeable in intensified unit operations constitutes
yet another highly attractive benefit of PI in a world where there is overwhelming
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