Examples of Intensified Processes

In the early part of the reaction the SDR offers no benefit since the reaction is not mass-transfer limited. However, at higher viscosities it was found that a single pass through the SDR at 200 °C gave a similar reduction in acid value (measure of the degree of polymerization) to a batch reaction time of between 40 and 50 min. By recycling the polymer 

The catalyst used was zinc triflate supported on silica, which was glued onto the surface of the SDR. Although total conversion could be achieved in a single pass, selectivity was highly dependent on residence time, increasing with shorter times. In a direct comparison with a batch process using the same catalyst at the same conversion and residence time a 200 times increase in throughput could be obtained. 

Several reactions have been demonstrated using microreactors. One of the potentially more important is the direct synthesis of MIC from oxygen and methyl formamide over a silver catalyst. Dupont have demonstrated this process using a microreactor cell similar to that described above in which the two reactants are mixed, then heated to 300 °C in a separate layer and subsequently passed through another tube coated with the silver catalyst. The estimated capacity of a single cell with tube diameters of a few millimetres is 18 tpa. 

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The combination of process intensification and process miniaturization is an important element of sustainable technology and a platform for advancement in multidisciplinary science and engineering. There are now several examples of intensified processes being utilized in industry, as apparent from patent activity. Some of these intensified processes are confined to a single unit operation, while others integrate several intensified unit operations in the more efficient production of existing/improved/novel products. 

In most of the attractive examples of intensified process equipment (e.g. in-line mixers, spinning disc reactors, rotating packed-beds, micro-reactors, etc.) the fluid residence time is measured in seconds. Therefore, a process designer should consider the use of these devices, provided that the reactions are (or can be made to be) completed in this time frame. If this is not the case, then the fluid intensity should be detuned to match the relatively relaxed kinetic environment. In this event, with a continuous process, a simple tubular reactor with very modest flow velocities could provide adequate plug flow and residence times up to several hours. In the case of a number of biological processes, as an alternative example, substantial intensification can be achieved using a continuous oscillatory baffled reactor (COBR, see Chapter 5), where residence times may be at best minutes and could extend to hours. 

One of the features of intensified process plant is the opportunity offered to combine a number of unit operations in a way that is not possible, or at best difficult, with conventional process equipment. The HEX-reactor discussed above is an example, where heat removal or addition is fully integrated with reaction(s) in a single package . It should be noted that a combination of unit operations usually represents process intensification in itself, regardless of the technology used, as significant overall redactions in capital cost, equipment size, etc., can be achieved. 

The first half of the chapter deals with broad issues leading up to installation, commissioning and operating plant, while the second part presents an example of a Process Intensification Methodology , in this case based upon Britest and BHR Group procedures (see below). In this case it is used to select an intensified chenucal reactor. 

Increasingly, guidelines resulting from political decision process of the European Union influence national markets and global competition. In order to have an influence on behalf of the interests of the plastics industry, the Association of Plastics Producing Industries, (VKE), is reported to wish to intensify its communication with European political institutions. The VKE sees the discussion about the EU book on the environmental problems relating to PVC as particularly controversial, and does not consider that it takes important points of view sufficiently into account. The treatment of the PVC theme, is examined as an example of so-called europisation of the work of associations. (Article translated from Kunststoffe 91 (2001) 4, pp.26-27). 

Appropriate combinations of boronic acid and fluorophores lead to a remarkable class of fluorescent sensors of saccharides (Shinkai et ah, 1997, 2000, 2001). The concept of PET (photoinduced electron transfer) sensors (see Section 10.2.2.5 and Figure 10.7) has been introduced successfully as follows a boronic acid moiety is combined intramolecularly with an aminomethylfluorophore consequently, PET from the amine to the fluorophore causes fluorescence quenching of the latter. In the presence of a bound saccharide, the interaction between boronic acid and amine is intensified, which inhibits the PET process (Figure 10.42). S-l is an outstanding example of a selective sensor for glucose based on this concept (see Box 10.4). 

The toolbox for process intensification is schematically shown in Figure 7. It includes process-intensifying equipment (PI hardware) and process-intensifying methods (PI software). Obviously, in many cases overlap between these two domains can be observed as new methods may require novel types of equipment to be developed and, vice versa, novel apparatuses already developed sometimes make use of new, unconventional processing methods. In Figure 7, examples of both PI hardware and PI software are shown. Many of them will be discussed in detail in other chapters of this book. Here, we give only a brief overview of the more important PI items. 

Examples of strategies for safe designs are prevent large volumes, intensify contact, reduce the need for aids (like solvents), use little intermediate storage. One can immediately see the similarities between intrinsically safe design and process intensification. This also means that applying process intensification techniques is beneficial for process safety. 

A good example of an intensified reactor for the model system is the Buss loop reactor concept as being offered by Kvaerner Process Technology (formerly Buss AG). This reactor is depicted in Figure 3. Reactor volumes range from 20 litres to 100 m3 in practice.3... 

In the example of the dehydrogenation reaction above, the mass flows are assumed invariant, their composition is not disturbed. Pressure and temperature are dictated by the thermodynamics of the system to attain a certain conversion of the feed. An alternative form of PI (process intensification) can be seen when one selectively removes one of the reaction products to shift the equilibrium and intensify the process. The combination of reaction and separation is a key example of PI. The literature aboimds with schemes to accomplish this. Its commercial use, however, is limited to a small number of cases. Following are examples, successful and not so successful, of this mode of operation ... 

Others have taken a broader look and have questioned the integration of the various steps prior to implementation of novel equipment. Examples of the intensihed equipment for hydrogen generation have been given above. In this section, we focus on describing the changes in the process flow scheme that have been proposed to intensify the operation. 

Clearly, as also indicated by Stankiewicz and Moulijn, there is a big overlap between the two areas. For instance, membrane reactors are an example of process-intensifying equipment (novel reactor) making use of process-intensifying methods (integration of reaction and separation). 

Basically the same conclusions are true for any intensified reactor. In case the intensified reactor allows a process to be heated with a small dT over the heat exchanger, but at the same time realises a substantial difference between solar supply and return temperature, there will be a high potential for heating the reactor with solar thermal energy with low-temperature collectors. This is further depicted in the next example, where an oscillatory flow reactor is analysed with gradual heating of the process medium. 

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