Multicomponent distillation continued

Steam Distillation—Continuous Flash, Multicomponent or Binary... 

Continuous multicomponent distillation simulation is illustrated by the simulation example MCSTILL, where the parametric runs facility of MADONNA provides a valuable means of assessing the effect of each parameter on the final steady state. It is thus possible to rapidly obtain the optimum steady state settings for total plate number, feed plate number and column reflux ratio via a simple use of sliders. 

MCSTILL - Continuous Multicomponent Distillation Column System... 

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... 

The general model was developed in Sec. 3.12. Table 5.8 gives a fairly general program for continuous multicomponent distillation. 

Kehlen, H., and Ratzsch, M. T, Complex multicomponent distillation calculations by continuous thermodynamics. Chem. Eng. Sci. 42, 221 (1987). 

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. 

Towler, Gavin P., and R. K Sinnott. ChemicalEngneering Design Principles, Practice, and Economics of Plant and Process Design. Boston Elsevier/Butterworth-Heine-mann, 2008. Chapter 11 examines continuous and multicomponent distillation, looking at the principles involved and design variations. Also discusses other distillation systems and components of a system. 

Residue Curve Maps. Residue curve maps are useful for representing the infinite reflux behavior of continuous distillation columns and for getting quick estimates of the feasibiHty of carrying out a desired separation. In a heterogeneous simple distillation process, a multicomponent partially miscible Hquid mixture is vaporized ia a stiH and the vapor that is boiled off is treated as being ia phase equiHbrium with all the coexistiag Hquid phases. 

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 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,... 

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... 

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. 

For a multicomponent liquid mixture with nc number of components, usually (nc-l) number of continuous columns will be necessary to separate all the components from the mixture. For a mixture with only 4 components and 3 distillation columns there can be 5 alternative sequences of operations to separate all the components (Figure 1.4). For a mixture with only 5 components, 4 distillation columns can be sequenced in 14 different ways. The number of alternative operations grows exponentially with the number of components in the mixture. These alternative operations do not take into account the production of off-specification materials or provision for side streams (this would further increase dramatically the number of columns and or operational sequences). 

The continuous distillation columns are designed to operate for longer hours (typically 8000 hrs a year) and therefore each column (or a series of columns in case of multicomponent mixture) is dedicated to the separation of a specific mixture. 

For single separation duty, Diwekar et al. (1989) considered the multiperiod optimisation problem and for each individual mixture selected the column size (number of plates) and the optimal amounts of each fraction by maximising a profit function, with a predefined conventional reflux policy. For multicomponent mixtures, both single and multiple product options were considered. The authors used a simple model with the assumptions of equimolal overflow, constant relative volatility and negligible column holdup, then applied an extended shortcut method commonly used for continuous distillation and based on the assumption that the batch distillation column can be considered as a continuous column with changing feed (see Type II model in Chapter 4). In other words, the bottom product of one time step forms the feed of the next time step. The pseudo-continuous distillation model thus obtained was then solved using a modified Fenske-Underwood-Gilliland method (see Type II model in Chapter 4) with no plate-to-plate calculations. The... 

When only one product (distillate) is produced in a continuous column using only one pass by processing a binary or a multicomponent mixture, the operation is defined as SPSS operation. In this type of operation the bottom product after the first pass is not processed further. Figure 11.3 shows the operation for a ternary mixture. Only one product (rich in component A) is obtained using one pass. 

When a number of products are produced sequentially using one pass to produce one distillate product from a binary or a multicomponent mixture in a continuous column, the operation is defined as SPSSS operation. For binary mixtures there will be a maximum of two distillate cuts, one being a specified product cut and the other being an off-specification product cut. Under such condition, of course, the final bottom product will be of specified purity. Figure 11.4 illustrates the operation for a ternary mixture. Here two passes are allowed in the same column sequentially. The first pass separates component A and the second pass separates component B. 

When a distillate product of specified purity is produced using a number of passes in a continuous column, the operation is defined as MPSSS operation. The number of distillate products depends on the number of components in the original mixture. This type of operation is used mainly to improve the recovery of a particular species in the feed mixture (see example section for further explanation). This type of operation can be applied to both binary and multicomponent mixtures. 

Comtant reflux, varying overhead composition. The reflux is set at a predetermined value at which it is maintained for the entire run. Since the pot liquid composition is changing, the instantaneous composition of the distillate also changes. The progress of the distillate and pot compositions in a particular binary separation is illustrated in Fig. 13-120. The variation of the distillate composition for a multicomponent batch distillation is shown in Fig. 13-121 (these distillate product cuts have relatively low purity). The shapes of the curves are functions of volatility, reflux ratio, and number of theoretical plates. The distillation is continued until the average distillate... 

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