Continuous processes batch concepts

Other established attempts on heat integration of batch plants are based on the concept of pinch analysis (Linnhoff et al., 1979 Umeda et al., 1979), which was initially developed for continuous processes at steady-state. As such, these methods assume a pseudo-continuous behaviour in batch operations either by averaging time over a fixed time horizon of interest (Linnhoff et al., 1988) or assuming fixed production schedule within which opportunities for heat integration are explored (Kemp and MacDonald, 1987, 1988 Obeng and Ashton, 1988 Kemp and Deakin, 1989). These methods cannot be applied in situations where the optimum schedule has to be determined simultaneously with the heat exchanger network that minimises external energy use. 

The concept of process intensification does not need to apply to the whole of an API production process. There is merit in looking at hybrid reaction schemes, which retain the benefits of, or capital investment in, batch equipment but use continuous processes for the generation of hazardous intermediates [17] or for certain unit processes. Of these, hydrogenation [18], filtration [19], phase separation [20], crystallisation [21] and drying [22] are good examples. 

Leuenberger H. New trends in the production of pharmaceutical granules the classical batch concept and the problem of scale-up. Eur J Pharm 2001 52 279. Leuenberger H. New trends in the production of pharmaceutical granules batch versus continuous processing. Eur J Pharm 2001 52 289. 

If the size of the production unit requires higher radiant power than can be provided, for technical reasons, by one lamp, clusters of light sources may be installed, which, consequently will alter the diameter or the height of the inner core of, for example, an annular photochemical reactor. However, following the check list of concepts (vide supra), optimal reaction conditions will in most cases limit the size of the photochemical reactor, and the planned rate of production may require several reactor units installed in a parallel mode (batch process) or in series (continuous process). 

One case study within the framework of this project is thus to test the concept of a micro structured reactor plant by applying the fast reaction of the enantioselective synthesis via organoboranes yielding chiral-substituted alcohols. This is typically a batch process carried out in the laboratory using conventional glassware and in the present case has been converted into a continuous process carried out by micro structured devices. This set-up has been used to characterize the physical properties of the backbone system. 

The batch concept offers the advantage that a well-defined and limited amount of product is being processed (characterized by the batch number) and, as a finished product, the entire batch can be accepted or rejected. In the case of a continuous production process, batch definition is less obvious and one has to look for an acceptable compromise related to this definition (e.g., the amount of product manufactured within a certain period). 

As the batch size of a continuous process is not well defined, Leuenberger " and Betz, Junker-Biirgin, and Leuenberger developed a quasi-continuous production concept. This concept, developed in cooperation between the Institute of Pharmaceutical Technology (University of Basel, Switzerland), Glatt (Pratteln,... 

Recent developments are related to both batch and continuous processes, including environmental monitoring (see Chapter 18). Applications in relatively inaccessible zones such as explosive, nuclear or high-temperature containments require new specific components and a control organization, revealing the considerable repercussions on the structure of future plants. This section attempts to summarize the most significant research of the past few years on remote control of chemical processes. The new concepts, multi-point measurement techniques, associated components, and aspects of real-time measurement techniques are also examined. 

In Section 13.3.1, the concept of batch/reactor residence time was presented. For batch/semibatch processes, batch time is often simply dictated by the maximum polymerization rate possible for a given piece of equipment and the time required to reduce monomer residuals or end groups to within speciflcation. For a continuous bulk or solution process, reactor residence time is simply a function of the size of the vessel and how fast monomer can be pumped... 

The above deliberations culminate in a separation concept which can be broken down into individual unit operations. Initially, these operations can be examined in the laboratory either on a batch basis, or in a continuous process to determine whether they are feasible in principle (e.g., are azeotropes formed , how difficult is separation , what is the dissolution rate , can the phases be separated , etc.). This gives the initial process concept, which can be used as a basis for starting the actual process development. 

Some manufacturers have looked for ways to achieve both scale advantages and support a large portfolio of variants. This can be done with a concept known as late product differentiation. Here, the majority of the ingredients are consolidated in a few base formulations and the bases are then topped off with key differentiating ingredients, dyes, and perfumes. This concept can be used with either batch or continuous processes depending on the application. 

It is clear from the above classification that batch processes are usually of the isolated or closed type, whereas the continuous processes are usually of the open type. As can be seen from the above definitions, the system theory is very abstract and, in general, it treats any system regardless of whether a mathematical model for this system can be built or not mathematical modeling, on the other hand, is less abstract and more applied than the system concept. 

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