Multistage backmixing

Figure 3.38. Multistage extraction cascade with backmixing of both phases.

Figure 3.39. Stage n of a multistage extraction cascade with backmixing.

Although more complex in form, the resulting model equations provide no major additional difficulty, and solution is also easily obtained. Multistage extraction with backmixing is covered in the simulation example EQBACK. 

Figure 3.49. Multistage mixer-settler cascade with entrainment backmixing. M and m refers to mixer and S and s to settler stagers are 1 to N.

Dynantics of Heat Exchangers, Simple Batch Extraction, Multi-Solute Batch Extraction, Multistage Countercurrent Ctiscade, Extraction Cascade with Backmixing, Countercurrent Extraction Cascade with Reaction, Absorption with Chemical Reaction, Membrane Transfer Processes... 

A stirred-tank flow reactor may be single-stage or multistage. As an ideal backmix flow reactor, it is referred to as a CSTR or multistage CSTR this is treated in Chapter 14. Nonideal flow effects are discussed in Chapter 20. 

Assuming the liquid phases remain immiscible, the modelling approach for multicomponent systems remains the same, except that it is now necessary to write additional component balance equations for each of the solutes present, as for the multistage extraction cascade with backmixing in Section 3.2.2. Thus for component j, the component balance equations become... 

EQBACK - Multistage Extractor with Backmixing System... 

Nagata, et al. (Nl, N2), Kawamura et al. (K4), and Yagi and Miyauchi (Y2) have studied the characteristics of various impeller agitated multistaged vessels. Such vessels were assumed to be a succession of plug-flow and backmix units, whose relative sizes were a function of the impeller speed. The parameter of the model, the fraction of total volume in a plug-flow, could also be related to a dispersion coefficient. Verification of the model was then obtained with kinetic experiments. 

M.S. Takriff, Column Flooding, Gas Holtkip and Interstage Backmixing of an Aerated Multistage, Machanically Agitated, Compartmented Column, PhD Dissertation, University of Arkansas, 1996. 

M.S. Takriff, W.R. Penney, and J.B. Fasano, Interstage backmixing of an aerated multistage, mechanically-agitated compartinented columns, Can. J. Chem. Eng., 76, 365-369 (June 1998). 

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