Flow Intensification

Elow intensification is made with the use of apparatuses in which flow follows a perfect plug flow the internal parts of the reactor have to be designed accordingly. Indeed, dead zones, that is, reactant accumulation, must be avoided not only in order to have better selectivity and yield but also to avoid formation of hot spots, which would generate safety problems. 

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Based on the study of process characteristics and predicting the possible results of technological flow intensification, the advanced technological flow sheet for the synthesis of saturated copolymers of ethylene and propylene, and unsaturated copolymers of ethylene, propylene, and a third monomer, have been proposed. 

Snaddon, R. W. L. and P. W. Dietz. Interstitial Flow Intensification within Packed Granular Bed Filters Experiments and Theory. Ind. Eng. Chem. Fundam. 23 (l98l+) ll+7 153. 

USP-grade anhydrous magnesium carbonate is used as a flavor impression intensification vehicle in the processed food industry (see Flavors and spices). Basic magnesium carbonates are used as free flowing agents in the manufacture of table salt, as a hulking agent in powder and tablet pharmaceutical formulations, as an antacid, and in a variety of personal care products (see Pharmaceuticals). 

Large fractional hole area, long flow path relative to tray spacing and high liquid flow rate are the key factors leading to the formation or intensification of vapor cross-flow channeling on sieve and valve trays. 

Cheng, A.T.Y. (1997) A high-intensity gas-liquid tubular reactor under supersonic two phase flow conditions, in Process Intensification in... 

For the sake of developing commercial reactors with high performance for direct synthesis of DME process, a novel circulating slurry bed reactor was developed. The reactor consists of a riser, down-comer, gas-liquid separator, gas distributor and specially designed internals for mass transfer and heat removal intensification [3], Due to density difference between the riser and down-comer, the slurry phase is eirculated in the reactor. A fairly good flow structure can be obtained and the heat and mass transfer can be intensified even at a relatively low superficial gas velocity. 

Strictly, chemical micro processing, in addition to being a device field based on micro channels, is a means to use micro flows, which is oriented not at one, but rather at a multitude of purposes. Process intensification, also strictly, is a concept (but specifying no concrete means) and apparatus for a specific purpose (see above). 

In practice, the process regime will often be less transparent than suggested by Table 1.4. As an example, a process may neither be diffusion nor reaction-rate limited, rather some intermediate regime may prevail. In addition, solid heat transfer, entrance flow or axial dispersion effects, which were neglected in the present study, may be superposed. In the analysis presented here only the leading-order effects were taken into account. As a result, the dependence of the characteristic quantities listed in Table 1.5 on the channel diameter will be more complex. For a detailed study of such more complex scenarios, computational fluid dynamics, to be discussed in Section 2.3, offers powerful tools and methods. However, the present analysis serves the purpose to differentiate the potential inherent in decreasing the characteristic dimensions of process equipment and to identify some cornerstones to be considered when attempting process intensification via size reduction. 

Concerning function integration, for example, micro-flow membrane reactors can exhibit similar process intensification, as shown already for their large-scale counterparts [75]. Separation columns for proteomics, immobilizing enzymes, utilize the large surface-to-volume ratios. Surface tension differences can guide and transport liquids selectively. 

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. 

Burns, J. R., Ramshaw, C., The intensification of rapid reactions in multiphase systems using slug flow in capillaries. Lab. Chip 1 (2001) 10-15. 

In recent years, micro-structured reactors have attracted considerable attention for a variety of applications [61, 62]. Such micro devices are characterized by a laminar flow, and the very high surface-to-volume ratio they provide leads to increased mass and heat transfer, offering the potential for process intensification. 

Similar analysis can be made for other types of materials. Thus, as a generalization, the curvature of a surface causes field intensification, which results in a higher current than that on a flat surface. Although the detailed current flow mechanism can be different for different types of materials under different potentials and illumination conditions, the effect of surface curvature on the field intensification at local areas is the same. The important point is that the order of magnitude for the radius of curvature that can cause a significant effect on field intensification is different for the substrates of different widths of the space charge layer. This is a principle factor that determines the dimensions of the pores. 

It should be pointed out that many biphasic systems have found their way into the chemical industry, starting from PTC and continuous flow (CF) processes. The reasons are that efficiency can be increased (rates, selectivity, energy requirements, reaction intensification), making them more economic and often more environmentally compatible, in short, more sustainable. 

This brought a bout a keen interest in other methods of intensification in processing. Lately, the directed effect of physical (mechanical) fields on molten polymers has become one such area. These effects, as demonstrated in many works published in the 1970s and in the 1980s, (see for examples [6-9]) result in altered parameters of micro- and macrostress of the system. Molding under conditions of directed physical fields, in particular, in the case of mechanical and acoustic vibration effects upon melts, is performed so that an additional stress superimposed on the polymer s main shear flow and the state of material is characterized by combined stress. 

The internal used in this work has good performance in intensification of gas-liquid mass transfer and in improving the flow distribution, and has a good perspective in application in airlift reactors. Meanwhile, further study on the internal should be carried out. 

Process intensification also offers substantial improvements to those sectors of the chemical industry in which time to market plays a crucial role, e.g., the fine chemical and pharmaceutical sectors. Ramshaw (35) discussed how process intensification could shorten the time to market in case of a low-tonnage pharmaceutical process. The idea consists in developing a continuous lab-scale process and using it directly as the commercial-scale process. One must not forget that liquid flow of only 1 milliliter per second means, in continuous operation, circa 30 tons per year, which is quite a reasonable capacity for many pharmaceuticals. 

Thonon B, Mercier P. Flow structure, thermal and hydraulic performances of compact geometries used as integrated heat exchanger reactor. Process Intensification Conference, Antwerp, October 1999. 

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