Process intensification conventional

Process intensification is commonly defined as Technologies and strategies that enable the physical sizes of conventional process engineering unit operations to be significantly reduced. This is achieved through ... 

In chemical micro process technology there is a clear dominance of pressure-driven flows over alternative mechanisms for fluid transport However, any kind of supplementary mechanism allowing promotion of mixing is a useful addition to the toolbox of chemical engineering. Also in conventional process technology, actuation of the fluids by external sources has proven successful for process intensification. An example is mass transfer enhancement by ultrasonic fields which is utilized in sonochemical reactors [143], There exist a number of microfluidic principles to promote mixing which rely on input of various forms of energy into the fluid. 

This class is the simplest of all micro reactors and certainly the most convenient one to purchase, but not necessarily one with compromises or reduced fimction. HPLC or other tubing of small internal dimensions is used for performing reactions. There are many proofs in the literature for process intensification by this simple concept. As a micro mixer is missing, mixing either has to be carried out externally by conventional mini-equipment or may not be needed at all. The latter holds for reactions with one reactant only or with a pre-mixed reactant solution, which does not react before entering the tube. 

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

Micro mixer elements, micro mixers and micro structured mixers typically have flows in the ml h-1, 11 h-1 and 1000 1 tf1 ranges, respectively, thus covering the whole flow range up to the conventional static mixers and being amenable to analysis and chemical production as well (see Figure 1.4). When used at the upper flow limit, microstructured mixers can act as process-intensification (PI) equipment. 

The introduction of membrane contactors in industrial cycles might represent an interesting way to realize the rationalization of chemical productions in the logic of the process intensification. Membrane contactors are, in fact, highly efficient systems for carrying out the mass transfer between phases and achieving high removals. They also present lower size than conventional apparatus. Commercial applications are already present (e.g., the electronics industry or bubble-free carbonation lines), however, some critical points must be still overcome and several are the research efforts needed for their further implementation at industrial level, as summarized below ... 

Membranes and membrane processes are best suited in this context as their basic aspects well satisfy the requirements of process intensification for a sustainable industrial production. In fact, they are precise and flexible processing techniques, able to maximize phase contact, integrate conversion and separation processes, with improved efficiency and with significantly lower energy requirements compared to conventional techniques. 

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. 

Many conventional wastewater treatment processes that have long been in use are now considered impractical because they require a large amount of space, a large number of unit operations, and are affected by problems associated with odor and other emissions. Recent years have seen an increasing trend toward process intensification, which has led to the development of advanced membrane processes that are simple to construct and operate, have well-defined flow patterns, better dispersion effects, relatively low power consumption, lower emissions, and high mass-transfer performance, which are compact and recyclable. 

Wu et al. [19] have analyzed the intensification of industrial mixing. An important element for process intensification is to increase mixing rate, heat transfer rate and mass transfer rate. A range of methods have been reviewed by Wu et al. [19], for both conventional stirred reactors and alternative forms of reactors, all with the aim of achieving process intensification through enhanced mixing, heat and mass transfer. 

Process Intensification provides a new incentive in the assessment of chemical processes. In this report a gas-liquid reaction forms the basis of a comparison between conventional and novel reactor concepts. The considered reaction can be applied in all of the described reactor concepts, in some cases however a process modification is needed. For the application of Process Intensification a good insight is required for both the reaction as well as the tools (reactor systems) in which the reaction is being applied. Regarding the novel reactor concepts however design data are scarce, which induces uncertainties to come to a correct validation of the potentials. 

Micromixers have been developed for flows ranging from < 1 mL h up to 10 000 L h At the low flow range, only single elements of the micromixer are required. These are often used in integrated systems for credit card sized fluidic chips [65]. For flows > 1 L h microstructured mixers are used for process intensification in pilot- and conventional-scale applications [65]. 

The revamping and retrofitting in the chemical, pharmaceutical and fine-chemical industries involve the innovative use of mostly conventional equipment and processes. An emerging area, namely, process intensification, offers additional methods. This chapter deals with this emerging area and its role in retrofitting and revamping. 

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