Micromixers types

Since different types of micromixers have different operating conditions, this chapter considers and discusses various micromixer types separately. Depending on the particular mixer types, attention is paid to a number of operating parameters such as R nolds number (Re) and Pedet number (Pe). The R nolds number... 

Each stage of particle formation is controlled variously by the type of reactor, i.e. gas-liquid contacting apparatus. Gas-liquid mass transfer phenomena determine the level of solute supersaturation and its spatial distribution in the liquid phase the counterpart role in liquid-liquid reaction systems may be played by micromixing phenomena. The agglomeration and subsequent ageing processes are likely to be affected by the flow dynamics such as motion of the suspension of solids and the fluid shear stress distribution. Thus, the choice of reactor is of substantial importance for the tailoring of product quality as well as for production efficiency. 

Schenk, R., Donnet, M., Hessel, V., Hofmann, H., longen, N. and Lowe, H., 2001. Suitability of various types of micromixers for the forced precipitation of calcium carbonate. In 5th International Conference on Microreaction Technology (IMRET 5), Strasbourg, France 27-30, May 2001. 

In Section 5.6, Lagrangian micromixing models based on mixing environments were introduced. In terms of the joint composition PDF, nearly all such models can be expressed mathematically as a multi-peak delta function. The principal advantage of this type of model is the fact that the chemical source term is closed, and thus it is not necessary to integrate with respect to the joint composition PDF in order to evaluate the... 

Af-Acyliminium ions are known to serve as electron-deficient 4n components and undergo [4+2] cycloaddition with alkenes and alkynes.15 The reaction has been utilized as a useftil method for the construction of heterocycles and acyclic amino alcohols. The reaction can be explained in terms of an inverse electron demand Diels-Alder type process that involves an electron-deficient hetero-diene with an electron-rich dienophile. Af-Acyliminium ions generated by the cation pool method were also found to undergo [4+2] cycloaddition reaction to give adduct 7 as shown in Scheme 7.16 The reaction with an aliphatic olefin seems to proceed by a concerted mechanism, whereas the reaction with styrene derivatives seems to proceed by a stepwise mechanism. In the latter case, significant amounts of polymeric products were obtained as byproducts. The formation of polymeric byproducts can be suppressed by micromixing. 

A slit-type interdigital micromixer was used for fast mixing [30] and compared to a tubular reactor and five Kenics mixers connected in series. Details on further components of the micromixer rig were not given, but most likely a capillary reactor was added for efficient heat exchange. 

In a detailed process optimization study, the impact of the type of micromixers and process parameters was determined [56]. As a result, a pilot with a Toray Hi-mixer connected to a shell and tube microheat exchanger was constructed. Continuous operation for 24 h was carried out to obtain pentafluorobenzene (PFB) after protonation (92% yield). In this time, 14.7 kg of the product was produced, that is, about 5 t/a. Thus, the industrial-scale production carried out using a batch reactor (10 m3) can be replaced by adding only four microflow systems of the scale investigated. The pilot plant produces 0.5 kg in 6h continuous operation, thus about 730kg/a (see Figure 5.19). The name of the industrial company was not disclosed. 

As industrial relevant Friedel-Crafts reaction, the synthesis of Bisphenol-F, a material for epoxy resin, from phenol and formaldehyde was chosen [57]. This reaction involves formation of higher order condensates such as tris-phenols. To minimize the latter, the molar ratio of phenol to formaldehyde is set to a very high value (30-40), which is more than 15 times larger than the amount theoretically necessary. Three types of micromixers were used. These are a T-shaped mixer with 500 pm inner diameter, a multilaminating interdigital micromixer with 40 pm channels and a so-called self-made K-M micromixer with center collision mixing. 

Second-order reactions provide the simplest example of nonlinear kinetics, where micromixing limitations have significant effects on reactant conversion. We use the two-mode model to determine the same for a typical bimolecular second-order reaction of the type... 

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