## And packed columns

The fundamental relationships required to describe the mass transfer which occurs on the plate of a distillation column are the same relationships required to describe the mass transfer which occurs in a packed distillation column. For many years, packed columns were used primarily for corrosive applications where ceramic packing was advantageous and for small-diameter columns where it was inconvenient to install plates. Because of the favorable economics of installation and low pressure drop,...

## Problems

8-1 (a) Obtain the expression for dFj drjk (b) Develop the formulas needed to evaluate dyjdrj and d ( drik by use of the calculus of matrices. (c) Develop the formulas needed to evaluate dVj drik and dLj dt k by use of the calculus of matrices. 8-2 For the first-order unidirectional reaction which occurs in the liquid phase develop the expressions for Rj and dRjjdr k. 8-3 Develop the complete set of equations for the application of the N(r + 2) Newton-Raphson method to conventional distillation...

## Distillate Rate D

Figure 10-3 Variation of the distillate rate D at a fixed reflux rate, I, 125. A Continuous Distillation Column at Total Reflux in the Rectifying Section D 0, B F, and Lx Finite Number In addition to the above specifications, it is also supposed that the following variables and operating conditions are fixed the number of stages N, the feed plate location f9 the model for the feed plate behavior, the complete definition of the feed (the composition, flow rate, and thermal condition), and the...

## Estimation Of The Fugacity Coefficients For The Vapor Phase Of Polar Gas Mixtures

The use of the virial equation of state and the correlations of Pitzer and Curl15,48,49 for the prediction of fugacity coefficients for nonpolar mixtures is presented first and then the method is extended to polar gas mixtures. Prediction of the Fugacities Coefficients for Polar and Nonpolar Mixtures In order to compute f P or f Pyi, by the truncated virial equation of state (see Table 14-8), it is necessary to evaluate the second virial coefficient B. There follows a summary of the formulas...

## Valve Trays

Valve trays have essentially all of the advantages of both bubble-cap trays and sieve trays but hardly any of the disadvantages. They have about the same capacity, efficiency, and low pressure drop offered by sieve trays. Like bubble-cap trays, valve trays can be operated over a wider range of operating conditions (including very low flow rates) than sieve trays. The relatively simple construction of valve trays leads to a cost which is not a great deal higher than the comparable sieve tray....

## LJ fe20

Application of the mean value theorems of integral and differential calculus followed by the limiting process wherein AZ and AW are allowed to go to zero yields + Ri 0 (0 < Z < ZTJ 0 < W < WT) (13-53) Separation of variables followed by integration from Z 0 to Z ZT at a given W yields Since KiXi does not change with Z at a given Wf this expression may be integrated and rearranged to give the definition of the modified Murphree point efficiency. em fl-yj+i.i j _ e-m (13_55) where n is...

## Eleven

Conventional and complex distillation columns at minimum reflux Two general classes of problems are solved in this chapter. These are perhaps best described by consideration of a conventional distillation column. The problems solved in Sec. 11-1 consist of those in which infinitely many stages are specified for the rectifying and stripping sections as well as the reflux and distillate rates (Lt and D), and it is required to find the corresponding product distribution. In Sec. 11-2 two...

## Equations Of State And Their Use In The Prediction Of K Values And Enthalpies

The equations of state which appear to be finding the widest application for distillation calculations consist of the modified versions of the Benedict-Webb-Rubin equation of state, the Soave-Redlich-Kwong equation of state, and the Peng-Robinson equation of state. All of the equations needed to compute the K values and enthalpies by use prthese equations of state are presented in this section. In addition an outlinethe development of the equations needed to compute the K values and enthalpies...

## Systems Of Columns

Two approaches exist for solving problems involving systems of columns, the column modular method and the system modular method proposed by Hess.15 In the column modular approach, the equations for each column of a system are solved in succession, and in the system modular approach, the complete set of equations for the system are solved simultaneously. While the system modular approach may be the ultimate method for solving problems involving systems of interconnected columns, the column...

## F[oi2 fNGi G2 Gy

The new function f0 corresponding to the new independent variable T0 for the reboiled absorber is introduced to express the condition that the specified values (V must be equal to the calculated value of V1 at convergence, that is, Figure 7-4 A system of an absorber and a distillation column with heat exchange between recycle streams and a trim heat exchanger. Figure 7-4 A system of an absorber and a distillation column with heat exchange between recycle streams and a...

## Multi Component Mixtures

The above concepts may be extended as demonstrated elsewhere.26 The critical temperature of the pseudoheavy component is given by the following extension of Eq. (14-106), namely, where component 1 is taken to be the lightest component of the mixture. The convergence pressure is given by an extension of Eq. (14-108), namely, Of these formulas, only the one for tcl given by Eq. (14-109) is used in the correlation which follows. The GPSA (Gas Processors Suppliers Association) charts as well as...

## The Unifac Method For Predicting Activity Coefficients

The UNIFAC method, developed by Fredenslund et al.21,22 is similar in concept to the ASOG method, but it is based on the UNIQUAC equation where the superscript C refers to the combinatorial part of the activity coefficient and the superscript R refers to the residual part of the activity coefficient. The combinatorial part of the activity coefficient is computed by use of the following expression In yf In 4- U In + I, - J Xjl (14-161) where Z, (z 2)(rf - qj - (r, - 1) vkiQk rt be vkiRk 0, xaJYj...

## Application Of The Theta Method Of Convergence To Distillation Columns In Which Chemical Reactions Occur

The 0 method of convergence, which was originally formulated for the solution of distillation problems in which chemical reactions did not occur, is extended to include the case where one or more chemical reactions occur on each stage of a distillation column. The computational time of the 0 method, which is one of the fastest known methods for solving distillation problems, is not significantly increased by the inclusion of one or more chemical reactions per stage. In the development which...

## Constants And Modifications Of The Benedictwebbrubin Equation Of State

Compilations of constants for the BWR equation of state have been given by several authors.The pure component constants given by Benedict et al.7 for the hydrocarbons (methane through M-heptane) yield accurate values of the properties at densities up to about 1.8 times the critical density. For temperatures well below the normal boiling points, constants are given by Orye.46 Also included in this compilation are constants for H2, N2, C02, and H2S. For temperatures 0.6 times the critical, Reid...

## Relationships Between The Partial Molar Quantities

Since Eq. (14-9) applies for both a mixture and a pure component, it may be differentiated termwise with respect to n, with P, T, and the remaining mole numbers held fixed to give The quantities G,, , , and S, are defined as follows J partial molar free energy (14-58) Hi ) partial molar enthalpy (14-59) Si l - partial molar entropy (14-60) Important thermodynamic relationships involving the partial molar quantities are as follows For ideal vapor and liquid solutions Proofs of the above...

## Mass Transfer Between Vapor And Liquid Phases

Four of the simplest and best known of the theories of mass transfer from flowing streams are (1) the stagnant-film model, (2) the penetration model, (3) the surface-renewal model, and (4) the turbulent boundary-layer model The stagnant-film model was proposed by Nernst28 in 1904. The model may be described by visualizing the passage of a gas stream containing components A and B past a liquid surface. Suppose that A is soluble and B is not soluble in the liquid. In this model, it is supposed...

## Storage Of Large Sparse Matrices

Large sparse matrices such as those encountered in Chap. 5 are commonly stored in computers in packed form, a term used to mean that only the nonzero elements are stored. Storage in packed form is almost essential because of the large amount of internal computer storage which would be required to store all of the zero elements. In order to avoid the storage of the zeros and to locate the nonzero elements in storage, the use of linked lists has become popular.7 The following information must be...

## Packed Distillation Columns

The packed column is now a widely used device for mass transfer in distillation, absorption, and stripping. Typical of the packings which are available today are those shown in Figs. 13-4 and 13-5. Recently, Bolles and Fair3 presented the results of an excellent evaluation of the design equations for packed columns. The most reliable equations or correlations for making the following types of determinations were determined. The equations and correlations for making these determinations are...

## Lewis And Whitman Principles Of Gas Absorption

Hirschfelder, and C. F. Curtiss Theoretical Calculation of the Equation of State and Transport Properties of Gases and Liquids, Trans. ASME, 76 1011 (1954). 2. R. B. Bird, W. E. Stewart, and F. N. Lightfoot Transport Phenomena, John Wiley and Sons, New York, 1960. 3. W. L. Bolles and J. R. Fair Performance and Design of Packed Distillation Columns, presented at the Third International Distillation Symposium, London, April, 1979, No. 213 of E.F.C., Sec. 3.3, p. 35, Institute of...

## Formulation Of An Almost Band Algorithm

For the case where one or more reactions occur on each stage of an absorber or distillation column and the vapor and liquid phases form highly nonideal mixtures, a formulation of the Almost Band Algorithm is recommended. In the present formulation for the case where one or more chemical reactions occur on each stage of an absorber, the following choice of N(2c + 1 + r) independent variables and N(2c + 1 + r) independent functions are made. In particular, for the case of one chemical reaction...

## Optimum Design And Operation Of Conventional And Complex Distillation Columns

Procedures for solving several types of optimization problems commonly encountered in the design and operation of conventional and complex distillation columns are presented. The continued increase in energy costs for operating distillation columns has created the need for rapid calculational procedures both for the design of new distillation columns and for the selection of optimum operating conditions for existing columns. Problems of the following types are solved 1 determination of the...

## Other Applications Of The Theta Methods

In the same manner that the capital 0 method was applied above to solve problems involving specifications other than the total flow rates, the 6 method for single columns may be applied to solve problems involving specifications other than the total-flow rates. To demonstrate this application of the 6 method, it is applied to conventional distillation columns for which the reflux ratio Lx D and the boilup ratio Vs B are specified instead of the reflux rate Lx and the distillate rate D. The...

## Conventional And Complex Distillation Columns At Minimum Reflux 377

Figure 11-4 Material-balance enclosures for the separated lights used in the 6 method of convergence and the Newton-Raphson methods. Figure 11-4 Material-balance enclosures for the separated lights used in the 6 method of convergence and the Newton-Raphson methods. material balances for the separated lights When the first balance encloses the top of the column and any stage r in the rectifying pinch and each of the other balances enclose the single stages, r, r 1, r 2, , - 1, , 5 - 2, and s 1...

## Info

T In the more recent editions, the vapor pressure of 704.5 mm for toluene at 108 C is inaccurately listed as 740.5 or 741 mm. t In the more recent editions, the vapor pressure of 704.5 mm for toluene at 108 C is inaccurately listed as 740.5 or 741 mm. Solution At T 80.02 C, PA 760, PB 300, and P 760. Then Eq. 1-5 gives _ P- PB _ 760 - 300 _ Xa PA- PB 760 - 300 Therefore at the temperature T 80.02 C, the curves T versus xA and T versus yA coincide at 1, 80.02 . At T 110.4 C, PA 1748, PB 760, and...

## Singlepass Sieve Trays With Crossflow

The single-pass sieve tray with crossflow appears to be the most widely used type of tray today. In a tray of this type, the vapor passes upward through the perforations or valves and then through the liquid on the tray. The liquid flows down through the column and enters each plate by flowing under the downcomer weir. Then the liquid flows across the plate and over the outlet weir and into the downcomer to the plate below as shown in Fig. 12-3. In order for the liquid to flow across each plate...

## Fortran H Extended

Consider first the case where the conventional distillation column has a partial condenser, and the condenser and reboiler duties Qc and QR are specified. The material and energy balance enclosures are the same as those shown in Figs. 11-4, 11-8, and 11-9. Except for stages 2 and N 1, the phase equilibrium functions are of the general form However, in the particular case of stage 2, the set v2appears in the component-material balances, but not the set 2i . Thus, the new set of variables X2i is...

## T4iMrb

Solution of Example 1-6 With the aid of the above equations, the number of plates required to effect the specified separation may be determined. To plot the operating line Eq. 1-37 for the rectifying section, the y intercept DXD Vr is computed in the following manner. Since Vr Lr D, and Lt Lr, it follows that PXD Xd _ 0.96 Q3 Vr Lr D 1 3.2 Since y2 XD for a total condenser , the point y2, X D lies on the 45 diagonal. The y intercept and the point y2, X D locate the operating line for the...

## Twelve

Tray design encompasses the determination of the column diameter and the tray spacing as well as a number of mechanical considerations. The scope of the material in this chapter is limited primarily to the fundamentals involved in the design of single-pass sieve trays. The fundamentals involved in the design of valve trays are essentially the same as those involved in sieve trays. No attempt is made to treat bubble-cap trays, since valve and sieve trays have been used extensively in new...

## Operating Characteristics Of Continuous Distillation Columns Over Wide Ranges Of Distillate And Reflux Rates

To determine the behavior of a distillation column over wide ranges of operating conditions, calculational procedures are needed for treating certain limiting conditions which arise such as D 0 and D F. Procedures are presented and discussed below. One of the more interesting results obtained in this section is shown in Fig. 10-3. Examination of this figure shows that as the distillate rate is varied from D 0 to D F at a fixed reflux rate Ll9 there exists a particular D 0 lt D lt F at which the...

## Separation Of Multicomponent Mixtures By Use Of One Equilibrium Stage

Each of the separation processes considered in Sees. 1-2 and 1-3 consist of special cases of the general separation problem in which a multicomponent mixture is to be separated into two or more parts through the use of any number of plates. The boiling-point diagram Fig. 1-6 is useful for the visualization of the necessary conditions required for a flash to occur. Suppose that feed to be flashed has the composition X xu xlf A and , and further suppose that this liquid mixture at the temperature...

## Weir Constriction Correction Factor

Figure 12-4 Height of vapor-free liquid in the downcomer of a single-pass sieve tray with crossflow. Figure 12-4 Height of vapor-free liquid in the downcomer of a single-pass sieve tray with crossflow. Figure 12-5 The correction factor for effective weir length. W. L. Bolles, Pet. Refiner, 25 613 1946 , by courtesy Hydrocarbon Process. Figure 12-5 The correction factor for effective weir length. W. L. Bolles, Pet. Refiner, 25 613 1946 , by courtesy Hydrocarbon Process. weir constriction...

## The Minimum Reflux Ratio By The 9 Method

The 0 method may be used to solve the classical problem in which the separations are specified for two components the light and heavy keys , and it is required to find the smallest reflux ratio Ll D required to effect the specifications. The smallest reflux ratio is achieved through the use of infinitely many stages in each section of the column. Consider first the case where the specifications bt dx and bh dh are made for a conventional distillation column. In addition, the column pressure,...

## Separation Of Heterogeneous Azeotropes

If the feed is in the two-phase region, the two phases may be separated and fed to each of two columns. Suppose that the boiling-point diagram for a mixture of components A and B is as shown in Fig. 6-8. The feed is introduced to the separator shown in Fig. 6-9 which operates at the temperature Tsep. Phase I is then fed to column 1 and phase II to column 2. The bottom products of columns 1 and 2 are relatively pure B and A, respectively. The distillate compositions are approximately those of...

## References

Sullivan, Jr. An Improved Algorithm for Solving Mass Balance Equations in Multistage Separation Processes, Can. J. Chem. Eng. 50 663 1972 . 2. D. S. Billingsley On the Equations of Holland in the Solution of Problems in Multicomponent Distillation, IBM J. Res. Dev., 14 33 1970 . 3. - On the Numerical Solution of Problems in Multicomponent Distillation at Steady State II, AIChE J. 16 441 1970 . 4. Brice Carnahan, H. A. Luther, and J. O. Wilkes Applied Numerical Methods....

## Qualitative Characteristics Of Azeotropic And Extractive Distillation Processes

Applications of azeotropiaand extractive distillation have continued to expand because many very close feiling mixtures may be separated economically by use of these techniques. The separation of such mixtures by conventional distillation methods is usually uneconomical because of the large number of stages which would be required to effect such separations. Because of the tendency toward nonideal behavior of mixtures, it is generally possible to find some component which when added to a given...

## Water

Figure 6-1 Separation of a mixture containing acetone and methyl alcohol by azeotropic and extractive distillation. W. C. Hopkins and J. J. Fritsch, Chem. Eng. 51 8 361 1955 , by courtesy McGraw-Hill Book Company. Figure 6-1 Separation of a mixture containing acetone and methyl alcohol by azeotropic and extractive distillation. W. C. Hopkins and J. J. Fritsch, Chem. Eng. 51 8 361 1955 , by courtesy McGraw-Hill Book Company. Figure 6-2 Purification of methyl ethyl keytone by azeotropic and...

## The 2n Newtonraphson Method

When the Newton-Raphson method7 is formulated in terms of two independent variables per stage, the temperature 7 and the flow ratio Lj Vj, the resulting procedure is called the 2N Newton-Raphson method. Originally, this procedure was called the multi-0 method.16,17 When both the vapor and liquid phases form ideal solutions on each stage, this procedure is an exact application of the Newton-Raphson method. The IN Newton-Raphson method may be applied to any type of distillation column or to any...

## System Modular Formulation Of

2N 1 NEWTON-RAPHSON METHOD FOR A PIPESTILL The pipestill shown in Fig. 4-7 is used for the purpose of separating the hydrocarbon feed Ft into seven fractions Vl9 Wu W2,W3,W4,W5, L2S . The remaining feeds, F2 through F5, consist of steam which is used as the stripping medium. The stages are numbered down from the top of the main column. The condenser-accumulator section is assigned the number 1, the top plate the number 2, and the bottom plate of the main column the number 28. The stages of the...

## Development And Application Of The Theta Method Of Convergence To Conventional Distillation Columns

Three general methods for solving distillation problems are presented in this book. The first of these, called the 0 method of convergence Refs. 11, 12 is recommended for solving problems involving any type of distillation column provided that the mixtures do not deviate too widely from ideal solutions. For such columns, the 0 method is one of the fastest known methods Refs. 2, 3 . For columns which do not have both a reboiler and an overhead condenser, such as absorbers and reboiled absorbers,...

## Introduction To The Fundamentals Of Distillation

In this chapter, the fundamental principles and relationships involved in making multicomponent distillation calculations are developed from first principles. To enhance the visualization of the application of the fundamental principles to this separation process, a variety of special cases are considered which include the determination of bubble-point and dew-point temperatures, single-stage flash separations, multiple-stage separation of binary mixtures, and multiple-stage separation of...

## Fundamental Principles Involved In Distillation

To compute the composition of the top product D and the bottom product B which may be expected by use of a given distillation column operated at a given set of conditions, it is necessary to obtain a solution to equations of the following types Consider first the subject of equilibrium relationships. A two-phase mixture is said to be in physical equilibrium if the following conditions are satisfied Ref. 3 . 1. The temperature Tv of the vapor phase is equal to the temperature TL of the liquid...