Multi-purpose vessels

For multi-purpose vessels there will be a much larger number of possible relief scenarios. The worst case can be found using the methods above, but the process may be more time-consuming because many more possible scenarios are likely to be identified. Sometimes different relief systems may be specified for the different reactions that are carried out in a reactor, and the bursting disc must be changed to the correct one at the beginning of a campaign. A robust procedure is clearly needed to ensure that this occurs. - 

Whenever a new reaction is introduced into a multi-purpose reactor, an assessment of the adequacy of the relief system needs to take place. If necessary, the relief system will need to be modified before the new reaction begins to be used. At the same time, the adequacy of the new relief system for air other reactions that are performed in the reactor will need to be checked, especially if the modification involves an increase in relief pressure due to a higher operating pressure for the new reaction. 

It may be possible to minimise the time spent on relief system assessment and design if the basis of safety for a multi-purpose reactor can be changed to prevention rather than emergency pressure relief. For example, if it can be arranged for all the reactions to operate in semi-batch mode with no significant reactant accumulation, then the use of a trip system of sufficient integrity may provide a suitable basis of safety. (This may not always be possible.) 

This is a simplified idealised example to illustrate some of the points made in this Chapter. 

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The equipment supplier will therefore aim to offer versatile, multi-purpose equipment that can be used in a range of processes. Most of it will be stainless steel or glass lined, to avoid problems with contamination or corrosion. Wherever possible, a single reaction vessel is dedicated to one particular process, and usually each preparation is performed in a self-contained area. This situation has eased somewhat in recent years, and more multi-use equipment is being installed. There is still not the flexibility in equipment use that one might expect in comparison, say, with the dyestuffs industry, but there is a trend in that direction. 

The problem is often compounded because batch reactors are frequently multi-purpose rather than dedicated to one process. A single batch reactor may be used to carry out many different chemical processes, and for each reaction it is necessary to ensure that a runaway cannot occur — for example, by allowing the heat of reaction to exceed the cooling capacity of the vessel. 

The second important point is the new chance to perform small-scale production tasks in a dedicated plant and not in a multi-purpose plant. The continuous process becomes a serious competitor to multi-purpose processes. It is a known problem of multi-purpose-plants that only part of the installed equipment is in use. Manpower is needed to run the plant and to rebuild the plant for the next product. Plants containing microstructured devices can be designed for multi-purpose applications, but the range of difference in use is usually smaller, since a typical microreactor is less flexible than a batch vessel. The decrease in flexibility is usually small compared with... 

The campaigns in the FCPI are typically operated on a train/stream approach where a solid key reagent is introduced and a crystalline product is obtained. The average characteristics of a production campaign are presented in Table 13.4. Unit operations such as reaction, distillation, liquid-liquid extraction and crystallization are fundamental procedures in a multi-purpose train. A conventional batch vessel is able to perform all these operations, allowing flexibility and versatility in the production. 

Multi-purpose fire extinguisher (fire rating 5A/34B) - if vessel has in- board engine 1 Fire blanket (light duty) if vessel has galley or cooking area VHF Radio - fixed or hand held Bailer... 

The earliest microwave systems for analytical purposes were closed-vessel systems with a multi-mode cavity. The primary improvement over domestic units was the addition... 

As noted earlier, not all open-vessel systems (viz. those that operate at atmospheric pressure) are of the focused type. A number of reported applications use a domestic multi-mode oven to process samples for analytical purposes, usually with a view to coupling the microwave treatment to some other step of the analytical process (generally the determination step). Below are described the most common on-line systems used so far, including domestic ovens (multi-mode systems) and open-vessel focused systems, which operate at atmospheric pressure and are thus much more flexible for coupling to subsequent steps of the analytical process. On the other hand, the increased flexibility of open-vessel systems has promoted the design of new microwave-assisted sample treatment units based on focused or multi-mode (domestic) ovens adapted to the particular purpose. Examples of these new units include the microwave-ultrasound combined extractor, the focused microwave-assisted Soxhlet extractor, the microwave-assisted drying system and the microwave-assisted distillation extractor, which are also dealt with in this section. Finally, the usefulness of the microwave-assisted sample treatment modules incorporated in robot stations is also commented on, albeit briefly as such devices are discussed in greater detail in Chapter 10. 

Figure 20.2 Installation of dual-purpose outdoor (a) and indoor (b) cylindroconical vessels (CCVs) suitable for fermentation and lageiing. (1) Servicing platform. (2) Tank dome with fittings. (3) Insulation. (4) Cleaning in place inlet and spray ball. (5) Cooling zone for lagering. (6, 7) Cooling zones for fermentation. (8) Cone cooling zone. (9) Cone base. (10) Distribution panel with connection pipes. (11) Multi-way valve block.

The increased flexibility of open-vessel systems has promoted the design of new microwave-assisted sample treatment units based on focused or multi-mode (domestic) ovens adapted to the particular purpose. Regarding MAE, examples of these new units include the microwave-ultrasound combined extractor and the focused microwave-assisted Soxhlet extractor. 

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