Systematic design of an extractive distillation for maximum‐boiling azeotropes with heavy entrainers

Abstract

Extractive distillation is one of the most attractive approaches for separating azeotropic mixtures. Few contributions have been reported to design an extractive distillation for separating maximum-boiling azeotropes and no systematic approaches for entrainer screening have been presented. A systematic approach to design of two-column extractive distillation for separating azeotropes with heavy entrainers has been proposed. A thermodynamic feasibility analysis for azeotropes with potential heavy entrainers was first conducted. Then, five important properties are selected for entrainer evaluation. Fuzzy logic and develop membership functions to calculate attribute values of selected properties have been used. An overall indicator for entrainer evaluation is proposed and a ranking list is generated. Finally, the top five entrainers from the ranking list have been selected and use process optimization techniques to further evaluate selected entrainers and generate an optimal design. The capability of the proposed method is illustrated using the separation of acetone-chloroform azeotropes with five potential entrainers.

Design and control for a dividing‐wall column with a partial condenser for pretreating an industrial multi‐component reformed gasoline mixture

“…Adjusting the values of RV and RL is an effective way to decrease the heat duty Q c and Q r, which are the basics of the energy cost. RL and RV are defined as follows: where L 0 is the total liquid flowing out of the common rectifying section (column 2); L 1 is the liquid flowing from the common rectifying section (column 2) to the main separation section (column 4); V 0 is the total vapour flowing out of the common stripping section (column 3); and V 1 is the vapour flowing from the common stripping section (column 3) to the main separation section (column 4).…”

“…Design and control are two important engineering aspects of the DWC. Controlling a DWC is more difficult than conventional separation sequences, because of the complex nonlinear interaction between controlled variables and manipulated variables . There are eight manipulated variables in DWC, namely, the heat duty of the condenser ( Q c), distillate flow rate ( D ), bottoms flow rate ( F bot ), side stream flow rate ( S ), reflux flow rate ( L ) or reflux ratio ( RR ), vapour boil‐up ( V ), liquid split ratio ( RL ), and vapour split ratio ( RV ) .…”

“…Controlling a DWC is more difficult than conventional separation sequences, because of the complex nonlinear interaction between controlled variables and manipulated variables. [21][22][23][24] There are eight manipulated variables in DWC, namely, the heat duty of the condenser (Qc), distillate flow rate (D), bottoms flow rate (F bot ), side stream flow rate (S), reflux flow rate (L) or reflux ratio (RR), vapour boil-up (V), liquid split ratio (RL), and vapour split ratio (RV). [25] Because the location of the fixed wall determines how the vapour flow splits between the two sides of the column, RV is not considered a manipulated variable in dynamic simulations.…”

“…As mentioned above, a four-point temperature control structure works well for the separation of ternary or quaternary mixture with a total condenser. [13,15,21,35,[47][48][49][50][51][52] However, research on control of a DWC with a five or more component feed is relatively scarce, and is usually encountered in pretreating an industrial multi-component reformed gasoline (IMCRG) mixture. IMCRG consists of non-aromatics, benzene, toluene, xylenes, ethylbenzene, and heavy aromatics.…”

Separation of acetonitrile/methanol/benzene ternary azeotrope via triple column pressure-swing distillation

“…Pressure-swing distillation (PSD) [14][15][16][17][18][19][20][21][22] avoids the potential problem of introducing the third component and has gained lots of attention from researchers in recent years, by comparison with special distillation such as extractive distillation (ED) [23][24][25][26][27][28], azeotropic distillation [29][30][31][32], and reactive distillation [33][34][35]. Munoz [36] studied ED and PSD process for isobutyl alcohol/isobutyl acetate separation using the commercial simulator Aspen HYSYS while Lladosa et al [37] investigated the separation of din-propyl ether and n-propyl alcohol and found that PSD was more attractive than ED using an entrainer.…”