Process intensification types

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. 

This is one order of magnitude higher than in conventional reactor types (1), which underlines the process intensification potential of monolithic reactors. 

In Table 3 the three common reactor types are compared. Obviously, the monolithic reactor in the Taylor-flow regime leads to a high degree of process intensification. When these numbers are recalculated into production rates, values of 40 mol/m3reactor-s were found. Figure 17 illustrates the high value in relation to the Weisz window of reality. This demonstrates the attractiveness of using monoliths in fast catalyzed gas-liquid-solid reactions. 

The overview in Table 1 holds, in principle, for any type of chemical industry. Additionally, different types of chemical industries may have different focuses, depending on their starting position and on their business requirements. Knowledge of the perspectives helps in determining the main cost drivers from the fist given in Table 1 and helps therefore in finding the starting points for process intensification studies. Table 2 presents an overview of some of the main types of chemical industries and the specific demands they posed on process intensification when applied in these industries. A distinction can thus be made between ... 

TABLE 2 Process Intensification for Different Types of Industries... 

This method has been applied within DSM for 13 of its existing processes from its three main business clusters (polymers and industrial chemicals, life science products, and performance materials). See Figure 4 for the scheme used within DSM that follows this route. The results showed possibilities for reducing the cost of the present processes to 60-90% of the current costs. (This was shown earlier, in Figure 5 of Chapter 1.) This shows that the way of performing process intensification studies described in this chapter can result in very economical results for various types of businesses (from life sciences to bulk chemicals). Two concrete examples are presented in the next section to give a feeling of process intensification. 

A wide range of dilferent reactor types e.g. continuous, membrane, bubble) have been used to perform large scale processes using alternative solvents. Conventional batch reactors and extraction vessels have been used in many cases. However, process intensification is moving forward hand in hand with alternative solvents and therefore engineering solutions often have an important role to play in this field. Nevertheless, these are not discussed at length in this chapter and will probably be the subject of another book within the green chemistry series. 

Process intensification is achieved by the superimposition of two or more processing fields (such as various types of flow, centrifugal, sonic, and electric fields), by operating at ultrahigh processing conditions (such as deformation rate and pressure), a combination of the two, or by providing selectivity or extended interfacial area or a capacity for transfer processes. In heat and mass transfer operations, drastic reduction in diffusion/conduction path results in equally impressive transfer rates. As the processing volume (such as reactor... 

Process intensification (PI) offers several opportunities to improve energy efficiency and reduce environmental impact [92]. Many chemical reactions currently carried out as batch processes in stirred tanks could be carried out in continuously operated, intensified reactors such as spinning disc or oscillatory baffle types. The plant used for separations can be made highly compact, and even for large-scale plants (nitric acid production) the concept of pocket-sized plant has been introduced to reduce energy needs in the process [93]. PI is thus a key element... 

Extremely widely practiced in industry, this type of mass transfer is at the basis of the absorption and distillation unit operations, two or three phase reaction systems and others. The magnitude of the gas-liquid interfacial area is, of course, of prime importance and this is where the process intensification opportunities for microtechnology mostly lie. Table 3.2, adapted from Ref [40], shows the potential... 

Fine chemicals are generally produced in large-scale batch reactors. However, in the past few years, a trend toward process intensification can be observed and more and more continuous production processes appear. Besides the advantage of a better reaction selectivity, these types of manufacturing processes also offer a lot of opportunities and challenges for engineers to combine continuous synthesis with a continuous purification method. 

Fractionation of liquid mixtures with supercritical carbon dioxide in counter-cur-rent columns can be operated continuously, because liquids can be easily pumped into and out of a column. This represents a big advantage over extrachon from solid materials, as it allows real process intensification - large quantities of feed can be processed with only a small volume under high pressure at any given time. Frac-tionahon, mostly of natural products or extracts, has been extensively studied at the laboratory and pilot-plant scale. The design principles of this type of column have been established, and scale-up procedures devised [1,6]. They can be operated with reflux, as in distillation, and frachonahon can therefore become an extremely se-lechve process. Difficult separahons can be effechvely carried out. 

Types of Process Intensification Physical and Phenomenon-Based Intensifications... 

The main aim of this chapter is to show the main applications of membrane technology in the petrochemical indns-try and the related current research trends, focusing on the impact that membrane technology can have on the process. In addition, a case study is provided to illustrate the analysis of a membrane process in terms of process intensification, showing the advantages that this type of design philosophy can transfer to an important indnstrial application. 

Gas-liquid-solid reactors with a trickle-flow regime are the most widely used type of three-phase reactors and are usually operated under steady-state conditions. The behavior of this kind of reactor under the other three-phase fixed-bed reactors is rather complex due to gas and liquid flow concurrently downward through a catalyst packing. For process intensification it is required to improve some of the specific process steps in such chemical reactors. Figure 4.1 shows an overview of different factors that influenced the trickle-bed reactor performance. 

Despite the fact that membrane technology already fulfills the concept of process intensification in some areas, especially in water desalination, fruit juice concentration and the petrochemical industry, effective application of these technology types at an industrial level still needs additional effort addressed at developing and integrating new materials, new design concepts, econonfics and process control, scale-up and realistic assessment of the basic working parameters on real pilot plants. 

---