Multicomponent Batch Distillation

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. 

STEAM - Multicomponent, Semi>Batch Steam Distillation... 

Continuous Multicomponent Distillation Column 501 Gas Separation by Membrane Permeation 475 Transport of Heavy Metals in Water and Sediment 565 Residence Time Distribution Studies 381 Nitrification in a Fluidised Bed Reactor 547 Conversion of Nitrobenzene to Aniline 329 Non-Ideal Stirred-Tank Reactor 374 Oscillating Tank Reactor Behaviour 290 Oxidation Reaction in an Aerated Tank 250 Classic Streeter-Phelps Oxygen Sag Curves 569 Auto-Refrigerated Reactor 295 Batch Reactor of Luyben 253 Reversible Reaction with Temperature Effects 305 Reversible Reaction with Variable Heat Capacities 299 Reaction with Integrated Extraction of Inhibitory Product 280... 

Bioremediation of Soil Particles 591 Spouted Bed Reactor Mixing Model 390 Steady-State, Two-Pass Heat Exchanger 515 Multicomponent, Semi-Batch Steam Distillation 508 Space-Time-Yield and Safety in a Semi-Continuous Reactor 365... 

The graphical-based shortcut methods for binary batch distillation may be applied to multicomponent distillation only when the separation is between two key components to produce one distillate product and the residue. In this case the calculations may be approximated by lumping the other components with either of the key components and treating the system as a pseudo-binary. 

This process is used extensively in the laboratory and in small production units where the same equipment can serve different applications. Between each batch operation, the equipment can be cleaned as necessary. When the charge is a multicomponent mixture, batch distillation in a single column can separate all constituents, whereas continuous distillation would require several columns. 

Figure 10-2 Approach of the steady state solutions for the start-up period of a batch column to the solution for a corresponding continuous column. [C. D. Holland, Unsteady State Processes with Applications in Multicomponent Distillation, 1966, by courtesy Prentice-Hall, Inc.]...

This chapter introduces how continuous distillation columns work and serves as the lead to a series of nine chapters on distillation. The basic calculation procedures for binary distillation are developed in Chapter 4. Multicomponent distillation is introduced in Chapter 5. detailed conputer calculation procedures for these systems are developed in Chapter 6. and sinplified shortcut methods are covered in Chapter 7. More complex distillation operations such as extractive and azeotropic distillation are the subject of Chapter 8. Chapter 9 switches to batch distillation, which is commonly used for smaller systems. Detailed design procedures for both staged and packed columns are discussed in Chapter 10. Finally, Chapter 11 looks at the economics of distillation and methods to save energy (and money) in distillation systems. 

Urmila M. Diwekar and K. P. Madhavan. Batch-dist A comprehensive package for simulation, design, optimization and optimal control of multicomponent, multifraction batch distillation columns. Comp. Chem. Eng., 15(12) 833-842, 1991. 

Example 10 Calculation of Multicomponent Batch Distillation A charge of 45.4 kg mol (100 Ih-mol) of 25 mole percent heuzeue, 50 mole percent monochlorohenzene (MCB), and 25 mole percent orthodichloro-henzene (DCB) is to he distilled in a hatch still consisting of a rehoiler, a column containing 10 theoretical stages, a total condenser, a reflux drum, and a distillate accumulator. Condenser-reflux drum and tray holdups are 0.0056 and... 

Differential Distillation—Simple Batch, Without Trays, Multicomponent Mixture... 

Batch with Constant Reflux Ratio, 48 Batch with Variable Reflux Rate Rectification, 50 Example 8-14 Batch Distillation, Constant Reflux Following the Procedure of Block, 51 Example 8-15 Vapor Boil-up Rate for Fixed Trays, 53 Example 8-16 Binary Batch Differential Distillation, 54 Example 8-17 Multicomponent Batch Distillation, 55 Steam Distillation, 57 Example 8-18 Multicomponent Steam Flash, 59 Example 8-18 Continuous Steam Flash Separation Process — Separation of Non-Volatile Component from Organics, 61 Example 8-20 Open Steam Stripping of Heavy Absorber Rich Oil of Light Hydrocarbon Content, 62 Distillation with Heat Balance,... 

MULTICOMPONENT BATCH DISTILLATION ASSUMPTIONS ARE THE SAME AS IN BSTILL EXCEPT THAT THE... 

Although this problem is one of multicomponent batch distillation, the product remains of constant composition so that normal methods can be used for plate-to-plate calculations at a point value of the varying reflux ratio. 

Wajge, R. M. and G. V. Reklaitis. An Optimal Campaign Structure for Multicomponent Batch Distillation with Reversible Reaction. Ind Eng Chem Res 37 (5) 1910-1916 (1998). 

Batoh distillation is frequently used for small-volume products. One column can be used to separate a multicomponent mixture instead of requiring NC — 1 continuous colimms. The energy consumption in batch distillation is usually higher than in continuous, but with small-volume, high-value products energy costs seldom dominate the economics. 

The model of a multicomponent batch distillation column was derived in Sec. 3.13. For a simulation example, let us consider a ternary mixture. Three products will be produced and two slop cuts may also be produced. Constant relative volatility, equimolal overflow, constant tray holdup, and ideal trays are assumed. 

There can be several alternative STNs for multicomponent mixtures depending on the number of main-cuts and off-cuts to be produced. The two basic modules of Figures 3.2 and 3.3 can be combined as many times as required to describe the entire operation. A few alternative STNs for ternary batch distillation are given in Figures 3.5-3.7 as the combination of these two basic modules. 

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