Azeotrope Batch distillation

Separation of n-hexane-ethyl acetate mixtures by azeotropic batch distillation with heterogeneous entrainers... 

Selection of a suitable entrainer for the separation of w-hexane-ethyl acetate mixtures by heterogeneous azeotropic batch distillation... 

New Configuration For Hetero-Azeotropic Batch Distillation I. Feasibility Studies... 

Despite the advances in the thermodynamics for predicting azeotropic mixture, feasible distillation boundaries, and sequence of cuts, the azeotropic batch distillation system is still incipient in terms of design, optimization, and optimal control. 

Urmila M. Diwekar. An efficient design method for binary azeotropic batch distillation. AIChE J., 37 1571 1578, 1991. 

Jayant R. Kalagnanam and Urmila M. Diwekar. An application of qualitative analysis of ordinary differential equations to azeotropic batch distillation. Artificial Intelligence in Engineering, 8 23-32, 1993. 

Even though the simple distillation process has no practical use as a method for separating mixtures, simple distillation residue curve maps have extremely usehil appHcations. These maps can be used to test the consistency of experimental azeotropic data (16,17,19) to predict the order and content of the cuts in batch distillation (20—22) and, in continuous distillation, to determine whether a given mixture is separable by distillation, identify feasible entrainers/solvents, predict the attainable product compositions, quaHtatively predict the composition profile shape, and synthesize the corresponding distillation sequences (16,23—30). By identifying the limited separations achievable by distillation, residue curve maps are also usehil in synthesizing separation sequences combining distillation with other methods. 

Open-loop behavior of multicomponent distillation may be studied by solving modifications of the multicomponent equations of Distefano [Am. Inst. Chem. Eng. J., 14, 190 (1968)] as presented in the subsection Batch Distillation. One frequent modification is to include an equation, such as the Francis weir formula, to relate liquid holdup on a tray to liquid flow rate leaving the tray. Applications to azeotropic-distillation towers are particularly interesting because, as discussed by and ihustrated in the Following example from Prokopalds and Seider... 

Efficient and economical performance of distillation equipment is vital to many processes. Although the art and science of distillation has been practiced for many years, studies still continue to determine the best design procedures for multicomponent, azeotropic, batch, raul-tidraw, multifeed and other types. Some shortcut procedures are adequate for many systems, yet have limitations in others in fact the same might be said even for more detailed procedures. 

Batch Distillation Evaporation and Condensation Continuous Distillation Fractionation Rectification Reflux Distillation Vacuum Distillation Steam Distillation Azeotropic Extractive Distillation Destructive Distillation Molecular Distillation Distillation by Compression and Sublimation)... 

Keywords Batch distillation Heterogeneous entrainer Azeotropic distillation... 

Process synthesis and design of these non-conventional distillation processes proceed in two steps. The first step—process synthesis—is the selection of one or more candidate entrainers along with the computation of thermodynamic properties like residue curve maps that help assess many column features such as the adequate column configuration and the corresponding product cuts sequence. The second step—process design—involves the search for optimal values of batch distillation parameters such as the entrainer amount, reflux ratio, boiler duty and number of stages. The complexity of the second step depends on the solutions obtained at the previous level, because efficiency in azeotropic and extractive distillation is largely determined by the mixture thermodynamic properties that are closely linked to the nature of the entrainer. Hence, we have established a complete set of rules for the selection of feasible entrainers for the separation of non ideal mixtures... 

For the synthesis of heterogeneous batch distillation the liquid-liquid envelope at the decanter temperature is considered in addition to the residue curve map. Therefore, the binary interaction parameters used in predicting liquid-liquid equilibrium are estimated from binary heterogeneous azeotrope or liquid-liquid equilibrium data [8,10], Table 3 shows the calculated purity of original components in each phase split at 25 °C for all heterogeneous azeotropes reported in Table 1. The thermodynamic models and binary coefficients used in the calculation of the liquid-liquid-vapour equilibrium, liquid-liquid equilibrium at 25 °C and the separatrices are reported in Table 2. 

I. Rodriguez-Donis, V. Gerbaud, X. Joulia, Entrainer selection rules for the separation of azeotropic and close boiling temperature mixtures by homogeneous batch distillation, Ind. Eng. Chem. Res 40 (2001) 2729-2741. 

R. Diissel, J. Stichlmair, Separation of azeotropic mixtures by batch distillation using an entrainer, Comp. Chem. Eng. 19 (1995) si 13— si 18. 

However, there are cases where none of these batch distillation columns can be used economically to improve conversion or yield. Also, complications typically arise if there are any azeotropes present in the mixture. 

For both the cryogenic crystallization or the polyazeotropic distillation, the diacetyl obtained by these routes may be good enough for most applications, with typical purities in excess of 96.8 % by weight (86.358 % by mole), but to satisfy market demands it is customary to polish the product by a final batch distillation. This step can readily remove small quantities of water and methanol as both of these possible impurities form low-boiling azeotropes with diacetyl. 

What has been said for the elimination of impurities of water applies analogously for the elimination of impurities of methanol. As both form low-boiling azeotropes with diacetyl, in actual fact water and methanol are eliminated together in the same final batch distillation. 

See destructive distillation batch distillation extractive distillation rectification dephlegmation flash distillation continuous distillation simple distillation reflux fractional distillation azeotropic distillation vacuum distillation molecular distillation hydrodistillation. 

Solvent dehydration Breaking azeotropes Batch and continuous pervaporation, vapor permeation—often coupled with distillation Hydrophilic, e.g., PVA polymer composite, ceramic Well-established... 

---