## Constant Molar Overflow Assumption

2.2.2 Constant molar overflow and other assumptions Constant molar overflow. This assumption is a substitute for the energy balances. It states that the mixture has a constant heat of vaporization and that sensible heat and heat of mixing effects are negligible. Equations (2.7) and (2.8) give a mathematical expression of this assumption. Detailed thermodynamic implications of this assumption are described elsewhere (e.g., Refs. 6-8). Generally, constant molar overflow holds well for systems...

## Y y

The above applies for a differential section. Integrating over a packed bed H feet tall At qg ae P r _ dy V Jo Jyia y* - y A more detailed derivation which spells out the assumptions is gives elsewhere (87,112,113). Number of transfer units (NTU). NTU is defined by Eq. (9.8). This is a measure of the difficulty of separation. Figure 9.16 illustrates thai concept. The NTU relates the change in bulk phase composition to tfc* average driving force. Height of transfer unit (HTU). The height of a...

## Info

The author believes that low-molecular-weight hydrocarbons refers to light hydrocarbons at atmospheric conditions or under vacuum. The foaming tendency of light hydrocarbon distillation at medium pressure (> 100 psia) is medium at high pressure (> 300 psia) is high. source Bolles, W. L. (Monsanto Company), private communication, 1977. The author believes that low-molecular-weight hydrocarbons refers to light hydrocarbons at atmospheric conditions or under vacuum. The foaming tendency of...

## D

Fnzn + Vn+1yn+1 + K. .y Vjn + Ljcn AH. + FJifjt + Vn+1Hv> tl + Ln.lHLji.i VnHVjx + L (2.3) Equilibrium Relationship In multicomponent distillation of j components, there are j - 1 component balances and j - 1 equations describing the equilibrium relationship. Multiple stages (Fig. 2.5b). Equations (2.1) to (2.4) apply to each stage. A rigorous solution (Chap. 4) simultaneously solves these equations for each stage and each component. The equations can be simplified and solved by analytical...

## Goodloe Packing Hetp

11.2 Structured Packings 11.2.1 Efficiency data plots Figures 11.1 to 11.10 and Table 11.2 contain published efficiency data for structured packings. Section 11.2.2 presents a procedure recommended by the author for applying these data. Section 11.2.3 is a legend for the comments in the right-hand column of Table 11.2. Unlike random packings, structured-packing HETP often rises with loads (Fig. 8.16c). HETP is measured at a constant reflux ratio (L V), usually at total reflux, so that vapor and...

## 9J O

Figure 6,25 Common flow regimes on distillation trays. bubbles, still with a very definite top or surface to the dispersion. Bubbles formed at the tray perforations rise unbroken to the top of the foam, and little bulk circulation occurs. The bubbles are distorted to polyhedra. This model is described in detail elsewhere (101,102). Cellular foam occurs at low vapor velocities in small columns, where the wall provides foam stabilization. It occurs with some systems or tray designs but not with...

## Ln fx

W0 moles originally changed to still Typically the right-hand side of Eq. (5.12) is evaluated by graphical integration, using the assumption that the vapor and liquid phases are in equilibrium. If the system to be separated is ideal or can be assumed to be ideal, relative volatility Eq. (5.6) is constant, and Eq. (5.7) can be used di rectly to compute equilibrium compositions. If the system is not ideal, experimental vapor-liquid equilibrium data must be available (see Chap. 2). Assuming the...

## L 620

Warning Minimum reflux ratios calculated by this method are somewhat lower than true values. This is because the method neglects the presence of light nonkeys just below the feed and heavy nonkeys just above it (see Sec. 2.3.6). 2.3.6 Key ratio piots and retrograde distillation Key ratio is the mole fraction ratio of the light key to the heavy key. Key ratio plots (Figs. 2.19, 2.20) plot key ratio in the liquid ULK i HK) against stage number on a semilog scale. The slope of each curve gives a...

## WoXn X0

Therefore, inserting Eq. (5.22) And again the right-hand side must be evaluated by graphical integration. Example 5.5 Using the values generated in the solution of Example 5.4, calculate the moles of vapor produced during the separation.

## Hd h9 AK h0J631ci

Equation (6.31c) is shown in Fig. 6.19. No weeping is predicted for points above the correlating curve, while weeping is predicted below it Weep rate prediction. Lockett and Banik (56) and Hsieh and McNulty (63) proposed correlations for predicting weep rates from sieve trays. Both correlations are based on pilot scale data, mainly with the air-water system. The Hsieh and McNulty correlation is based on a broader data bank, which includes the experimental data by Lockett and Banik. Hsieh and...

## Davfd R Gill

Simulation Sciences, Inc., Brea, California Interpolation of experimental flood, pressure drop, and maximum operational capacity (MOC) data is the most reliable and accurate method available for predicting flood, pressure drop, and MOC. As pointed out in Sees. 8.2.6 to 8.2.9, use of correlations to predict these parameters can lead to poor and dangerously optimistic results in many situations frequently encountered in commercial practice. This chapter presents an atlas of charts for...

## Hk

When relative volatilities vary, the equilibrium curve is a weak function of the reflux ratio because the operating temperature shows some dependence on the reflux ratio. In order to draw the equilibrium curve, first set the reflux ratio. Set vapor and liquid flow rates. Calculate the limiting compositions of the nonkeys using Eqs. (2.50) to (2.53). Determine the relative volatilities of the keys at several values of xe in the rectifying and stripping sections, by carrying out bubble-point...

## L Factor Robbins Correlation

Equation (8.13) states that pressure drop is the sum of two terms. The first term describes the friction loss through the packing, and is the only important term in the preloading regime and when Lf is below 20,000. Under these conditions, the pressure drop is proportional to the square of the gas rate. The second term describes the increase in the slope of the pressure drop with gas rate in the loading regime. Equation (8.13) applies only for Lf < , 20,000. Figure 8.20 is a graph of the...

## Packing materialrandom packings

Packing material selection is primarily based on the corrosion resistance. The factors below are also important. Reference 16 has an excellent detailed discussion. Metals. Carbon steel packings are usually the first choice for noncorrosive services. Compared to ceramic and plastic, they normally offer higher capacity and efficiency, a wider range of geometries, higher turndown, are unbreakable, and have a high compression resistance. Stainless steel packings cost roughly three to five times...

## E

Packing factor, values listed in Table 10.1, ft-1 Flow parameter, given by Eqs. 8.3 and 8.21 Dry-bed packing factor, values listed in Table 8.3, ft1 Froude number of the liquid. Given by Eq. 8.20 for the Bravo et al. pressure drop correlation, and by Eq. 9.18 for the Bravo and Fair efficiency correlation, dimensionless

## Calculations

Column process design specifies the separation, and sets column pressure, reflux, stages, and feed point. These in turn yield internal flows and reboiler and condenser duties. This chapter addresses the main column process design considerations. The column is optimized during the process design, and many times later during operation. Computer control continuously optimizes the column on-line. Both design and on-line optimization are also addressed in this chapter. Column process design proceeds...

## TLfd

Schmidt's correlation is sensitive to the contact angle estimate both in Eqs. 8.35 and 8.38 . Table 8.5 lists the range of applicability of Schmidt's correlation. The Schmidt correlation is based on data for Raschig and Pall rings 102 , mainly for positive-surface-tension systems 58 . Prediction by rule of thumb. Popular rules of thumb for minimum wetting rates in random packings are table 8.5 Range of Applicability of Schmidt's Minimum Wetting Rate Correlation 102 Liquid falling film number,...

## Performance with aqueoushighviscosityhighsurfacetension systems

Data in Chap. 11 see Figs. 11.2 and 11.4 to 11.6 show that many aqueous systems in structured packings give HETPs roughly twice those of nonaqueous systems. This does not occur in all aqueous systems for instance, the HETPs for methanol-water in Fig. 11.5, and for H20-D20 in Figs. 11.1 and 11.3, are well in line with those of nonaqueous systems. The exceptions may be explained by arguing that the above methanol-water tests were conducted at the methanol-rich end, and that the H20-D20 system,...

## G

Gas flow rate, lb h-ft2 Only in Fig. 8.17, units are lb s-ft Gf Gas loading factor in the Robbins pressure drop equation, de g Acceleration due to gravity, 32.2 ft sec2 gc Dimensional constant, 32.2 lb-ft lbf-s2 Ga Galileo number, given by Eq. 8.9 h Height of packing particle, in h Height of structured packing flow channel lt i.e., crimp height , in Ha Height of gas transfer unit, ft Hl Height of liquid transfer unit, ft kL Liquid holdup, ft3 liquid ft3 bed volume HETP Height equivalent of a...

## Flow Regimes on Trays 641 The common flow regimes

The classic hydraulic model Sec. 6.2.1 oversimplifies tray action. There are five main flow regimes on distillation trays 12,99 . These regimes Figs. 6.25 to 6.28 may all occur on the same tray under different liquid and vapor flow rates Fig. 6.29 . An excellent overview of the fundamentals and modeling of these flow regimes is presented by Lockett 12 . Bubble regime F g. 6.25a or deep pool occurs at low vapor velocities. Discrete noncoalescing bubble swarms rise through quiescent liquid, which...

## Koch Bulletin Ks-1

Fig iff 11.10 Published HETP data for Max-Pak nee Table 11.2 for curve identification , a Plotted against vapor load 6 plotted against liquid load. 1. Eckert, J. S., and L. F. Walter, Hydrocarb. Proc. amp Pet. Ref. 43 2 , p. 107, 1964. 2. Wu, K. Y., and G. K. Chen, I. Chem. E. Symp. Ser. 104, p. B225, 1987. 3. Billet, R., Distillation Engineering, Chemical Publishing Co., New York, 1979. 4. Billet, R., Chem. Eng. Prog. 63 9 , p. 53, 1967. 5. Billet, R., S. Conrad, and C. M. Grubb, 1. Chem. E....

## W 2945

It was recommended 12,56 that the clear liquid height hc in Eq. lt 6.33 be calculated using Colwell's 68 clear liquid height correlation Sec. 6.3.3 . The denominator of Eq, 6.33 contains the difference between liquid and vapor densities instead of the liquid density in the original Lockett and Banik correlation 56 . This modification, incorporated by Colwell and O'Bara 58 , has negligible effect at low pressure, but makes the correlation less conservative at high pressure. Colwell and O'Bara 58...

## Name Index

This index includes names of authors, packings, computer simulators, and the like. The most significant page references appear in boldface type. AlChE tray efficiency, 372-376, 382, 388, 389, 396 Akashah et al. optimum feed, 118, 119 Albright random cells, 542 AMSYM program, 171, 192 ASPEN system, 163 ASPENPlus system, 163, 177, 179, 187, 192 Ballast-plus ring, 427, 500, 601, 643, 661 638-641, 656-661 Ballast saddle, 426, 500, 596, 597, 641 Barker and Self eddy diflusivity, 373-375 Bell and...

## Strigle Packed Tower

Figure 8.18 Continued GPDC interpolation plots for structured packings flood points, d The Dolan, Hausch and Petschauer plot for Intalox 2T Structured Packing. Part d, from G.W. Hausch, P. Quotson, and K. Seeger, Structured Packing Revamp of a 306 Psig Depropanizer, paper presented at the AJChB Annual meeting, Los Angeles, California, November 1991 reprinted courtesy of the Norton Company. vacuum and low superatmospheric pressures, and when the appropriate constants are available, the Billet...

## T

Figure 6.26 Continued Tray action closeups in various flow regimes, c spray. Note the existence of gas jets at tray orifices orifice positions are marked . Dotted horizontal lines indicate positions of minimum and maximum in the vertical dispersion sensitivity profiles such as the spray profile shown in Fig. 6.286 . id Inclined gas bubbling under influence of a horizontal liquid flow, typical of the emulsion regime, part c from W, V. Pinczewski and C. J D. Fell, Trans. Inst. Chem. Engrs. London...

## Efficiency scaieup equipment factors

The operating regime on the tray governs tray efficiency 17,99,106-110,116,117,147 . Scaieup of efficiency data from one regime to another is therefore dangerous and should be avoided. Further, the test data must be at similar column loading to the prototype 18,135 . Scaieup from an existing commercial column. As long as data are for the same system under similar process conditions, loadings, and operating regime, this can give excellent efficiency predictions. If...

## Pressure drop inherent limitations and traps

Pressure drop This is often used to specify packed tower capacity. The application of this criterion, and the interpretation of packing pressure drop data are not trouble-free. Some inherent limitations and traps are 1. In small columns lt 3 ft in diameter pressure drop varies with tower diameter 3,56 . With random packings, the smaller the tower diameter, the lower the pressure drop, possibly due to enhancement of wall effects. Since the bulk of the published pressure drop data were obtained...

## Minimum Wetting Rate Of A Mellapax 250y

An implication of this observation is that it is important to follow good redistribution practices. If a tall bed is unavoidable, it may be beneficial to attempt using larger packings in it. 9. Liquid maldistribution lowers packing turndown 15,160,161 . The two upper standard distributor curves in Fig. 8.166 represent a progressively lower quality of initial liquid distribution. The diagram shows that packing turndown becomes progressively poorer with greater maldistribution. Figure 9.76...

## N

Figure 6.28 Characteristic features of the spray regime, a Generation of drops by tearing liquid sheets at tray orifices Part o from W. V. Pinczewski and C. J. D. Fell, Trans. Inst. Ckem. Eng. London , 52, p. 294, 1974. All parts reprinted courtesy of the Institution of Chemical Engineers, UK. Figure 6.28 Characteristic features of the spray regime, a Generation of drops by tearing liquid sheets at tray orifices Part o from W. V. Pinczewski and C. J. D. Fell, Trans. Inst. Ckem. Eng. London ,...

## 1

Figure 6.21 Dry pressure drop, a Discharge coefficients for gas flow in sieve trays. amp Typical valve tray pressure drop profile. Valves start to open at point A the closed balance point and are fully open at point B the open balance point . Part a from I. Leibson, R, E. Kelley, and L. A. Bullington, Pet. Ref., February 1957, p. 127, reprinted courtesy of Hydrocarbon Processing. Part b from George F. Klein, Chemical Engineering, May 3, p. 81, 1982, reprinted courtesy of Chemical Engineering....

## Geometrical features of corrugated structured packings

Corrugated structured packings are fabricated from thin, corrugated crimped metal sheets, arranged in parallel to each other. The surface of the corrugated sheets can be grooved, lanced, textured, or smooth. The corrugated sheets may be perforated or unperforated. The corrugated sheets are assembled into an element, typically 8 to 12 in talL The sheets in each element are arranged at a fixed angle to the vertical. Adjacent elements are rotated so that sheets of one element are at a fixed angle...

## Objectives For Maximizing Capacity

To maximize the void space per unit column volume This minimizes resistance to vapor upflow, and therefore, enhances packing capacity. A corollary is that for random packings, capacity increases with particle size Fig. 8.7 for structured packings, capacity increases with the space between adjacent layers, and for grids, capacity increases as the lattice openings are widened. Comparing to the first objective for maximizing efficiency, this corollary states that the packing size that maximizes...

## Considerations for specifying structured packings

Wire mesh packings easily plug and are best avoided altogether in solid-containing services. Corrugated-sheet packings, especially those with wider spacings between adjacent layers, are more tolerant to solids, but their distribution equipment may not be. If a potential for fouling exists, accurate data must be gathered and com- Figure 8.13 Flow of liquid over a vertical surface of Koch-Sulzer wire mesh left and metal sheet right . Reprinted courtesy of Koch Engineering Company, Inc....

## Flood point concept and traps

In 1966, Silvey and Keller 54 listed 10 different flood point definitions that have been used by different literature sources. A recent survey 59 listed twice that many. As Silvey and Keller pointed out 54 the existence of so many definitions puts into question what constitutes flooding in a packed tower, and at what gas rate it occurB. Symptoms used to identify flood in these definitions include appearance of liquid on top of the bed, excessive entrainment, a sharp rise...

## Secondgeneration Random Packings

Developed by the Norton Company, they superseded the Berl saddles. The shape of the Berl saddle was modified in the Intalox so that adjacent elements do not blank off any sig- Flgure 8.1 First-generation random packings, a Raschig ring, metal gt Lessing ring, metal c Berl saddle, ceramic. Flgure 8.1 First-generation random packings, a Raschig ring, metal gt Lessing ring, metal c Berl saddle, ceramic. Figure 8.2 Continued Second-generation random packings, c Super...

## Structured Packing Fp

10 0 30 40 50 70 100 Figure 8.12 Random versus structured packings, a Specific surface area versus packing factor. alone. Other factors Sec. 8.1.2 , such as spread of the surface ares, also affect efficiency. Figure 8.126 suggests that at low specific surfat areas lt 60 ft2 ft3 , these factors tend to favor random packings, Le, that a second- or third-generation packing is more efficient than a structured packing of the same specific surface area. The difference ia efficiency appears to widen...

## Colwell Correlation For Trays

The effective clear liquid height is given by The factor C is analogous to the Francis weir constant in Eq. 6.49 and is given by The froth density lt t gt is estimated by an expression analogous to Fig. 6.22a where Cs is the C-factor, given by Eq. 6.4 , with Cs and us based on the tray bubbling area. 6.3.4 Head loss under downcomer apron This head loss, required for downcomer backup calculation Sec. 6.2.71. is calculated for segmental downcomers from 2-5,18,31,32 Ada should be taken as the most...

## Floodpoint prediction

Sherwood-Eckert generalized pressure drop correlation GPDC . For several decades, the Sherwood-Eckert GPDC chart has been the standard of the industry for predicting flood points and pressure drops. This chart was initially developed by Sherwood et al. 68 . Sherwood's chart, later modified by Lobo et al. 69 , contained only a single curve that predicted packing flood points. Leva 70 retained the flood-point curve and added a new family of curves onto the chart to predict packing pressure drop....

## Structured packings versus random packings

Figure 8.12a compares random to corrugated sheet structured packing in terms of specific surface areas and packing factors. For random packings, the lines shown were taken from Figure 8.11 Continued Common corrugated-type structured packings. e Intaia Higb-Performance structured packing, lt f MAX-PAC . Port e, courtesy of Norton Company part f, courtesy of Jaeger Products, Inc. Figure 8.11 Continued Common corrugated-type structured packings. e Intaia Higb-Performance...

## Types of corrugated structured packings

Mellapak has grooved and perforated surfaces. Adjacent elements are rotated 90 . The crimp angle is 45 , and the crimp apex is sharp. Mellapak is available in several types. The Mellapak number denotes the nominal surface area of the packing per unit volume m2 m3 . The suffix denotes the angle of orientation to the vertical axis Y signifies 45 , X signifies 60 . For instance, Mellapak 250.Y has a surface area of 250 m2 m3, and a 45 angle of orientation to the vertical...

## Structured packing evolution

Structured packings have been around since as early as the 1940s. Early structured packings, such as Panapak 15 , never became popular. Perhaps these were not marketed aggressively enough, or perhaps they appeared before the detrimental effect of liquid maldistribution on structured packing was appreciated. First-generation structured packings are seldom used nowadays. The second generation of structured packings began in the late 1950s with high-efficiency wire-mesh packings such as Goodloe ,...

## Thirdgeneration Packings

Intalox Metal Tower Packing 0MTP Fig. 8.3a . IMTP combines the high void fraction and the well-distributed surface area of the Pall ring with the low aerodynamic drag of the saddle shape. Compared to the Pall ring, it provides a more open shape and improved liquid spread, while incorporating adequate mechanical strength and entanglement resistance 5 . IMTP is available in metals only. It is marketed exclusively by the Norton Company. Cascade Mini-Rings CMR Figs. 8.3b, 8.4a, 8.5a . These rings...

## Apparent J h J naj

Error in efficient - error in volatility lna 7.36 Figure 7.6 is a plot of Eq. 7.36 . At very low relative volatilities a lt 1.2 , small errors in VLE have a huge impact on tray efficiency. For instance, at a relative volatility of 1.1, a -3 percent error in relative volatility gives a tray efficiency 40 to 50 percent higher than its true value Fig. 7.6 . Since VLE errors are seldom lower than 2 to 3 percent, both tray efficiencies and packing HETPs of low-volatility systems become meaningless...

## Mcavy

Figure 6.17 Sieve tray weeping mechanisms. Reprinted with permission from M. J. Lockett and S. Banik, Ind. Eng. Ckem. Proc. Des. Dev., vol. 25, p. 561, Copyright 1986 American Chemical Society. Factors affecting weeping. Weeping tendency increases with Larger fractional hole area 4,39,56-63 . Larger liquid rate 26,56,63-65 . Taller weirs 28,48,63 . Lockett and Banik 56 observed that taller weirs increased the weeping tendency, except 1 at high liquid rates and high weirs 2 at high vapor rates,...

## P

The corrected distillate and bottoms component product rates are amp , 0 ib, cap, 4.48 where Pi is a corrector created by combining the overall component balance Eq. 4.45 with the definition of 6 Eq. 4.46 In the theta method, the total distillate rate and reflux ratio are all that can be specified and the theta function Eq. 4.50 is written to find a value of theta such that the sum of the corrected component distillate rates equals the total distillate rate fr- 2 1 0 lt 450 For complex columns,...

## Empirical prediction methods

Several empirical tray efficiency correlations are available in the literature. Of these, the O'Connell correlation has been the standard of the industry for several decades. The O'Connell correlation 149, Fig. 7.5a . This correlation is based on test data from 31 plant columns, including hydrocarbon, chlorinated hydrocarbon, and alcohol separation columns. It evolved from an earlier correlation by Drickamer and Bradford 160 , which empirically correlated efficiency test data for 54 refinery...

## Implications of the emulsion regime for design and operation

The difference in the behavior of the aerated mass between the emulsion and froth regimes is far less apparent than the difference between the froth and spray regime. Flow across the tray. In the froth regime the liquid is thrown over as drops and slugs, and therefore the flow does not obey the Francis weir formula 85,104 . In the emulsion regime a homogeneous dispersion flows over the weir. While in the froth regime the bubbles are of different sizes, in the emulsion regime most of the vapor...

## K hw kom hJ2620

Fedc ht hw how hA amp 6.21 Calculation of each of the individual terms in Eq. 6.21 is described in Sees. 6.3.1 to 6.3.4. The downcomer aeration factor 4 gt dc is defined by Eq. 6.18 . It describes the fractional volumetric liquid holdup in the downcomer. Mechanism. Vapor enters the downcomer with the froth that flows over the outlet weir. Additional vapor is entrained into the liquid due to the impact of the falling liquid on the liquid surface in the down-corner, in the same manner as a...

## Tray efficiency in multicomponent separations

In binary mixtures, the efficiencies of each of the two components are identical. In multicomponent separations, component efficiencies are all different because 1. Each component has a different diffusivity, both in the vapor and in the liquid. 2. In a multicomponent mixture, the diffusion rate of a component depends not only on its own concentration in the mixture, but also on the concentration of other components. This may lead to coupling and interaction of the mass...

## Tray Hydraulic Parameters 631 Pressure drop

The total pressure drop across a tray is the sum of the pressure drop across the disperser unit, hd dry hole for sieve trays dry valve for valve trays , and the pressure drop through the aerated mass hh i.e., The diy pressure drop across the disperser unit hd in Eq. 6.41 is given by a variation of the orifice equation Sieve trays. K in Eq. 6.42 is given by 4,5,18,30,31 The prime variables affecting the orifice coefficient, Cv are the fractional hole area and the ratio of tray thickness to hole...

## Effect of tray maldistribution on efficiency

The stagnant zones Fig. 7.76 Fig. 7.8a,6 have a detrimental effect on efficiency in large-diameter trays. The stagnant liquid composition reaches equilibrium with the rising vapor, and from then on changes no further. Vapor rising through stagnant zones undergoes no change in composition, and tray efficiency drops. A counteracting effect is that the stagnant zones receive fresh liquid from the neighboring active region Fig. 7.8c , and this reinstates mass transfer....

## References Chapters 6 and

Z., Distillation Operation, McGraw-Hill, New York, 1990. 2. Bolles, W. L., Pet. Process., Feb. 1956, p. 65 March 1956, p. 82 Apr. 1956, p. 72 May 1956, p. 109. 3. Bolles, W. L., in B. D. Smith, Design of Equilibrium Stage Processes, McGraw-Hill, New York, 1963. 4. Ludwig, E. E., Applied Process Design for Chemical and Petrochemical Plants, 2d ed., vol. 2, Gulf Publishing, Houston, 1979. 5. Van Winkle, M., Distillation, McGraw-Hill, New York, 1967. 6. Yanagi, T., Chem. Eng.,...

## Sieve Tray Aeration Factor

Klein, Chemical Engineering, May 3, p.81, 1982, reprinted courtesy t Chemical Engineering. source George F. Klein, Chemical Engineering, May 3, p.81, 1982, reprinted courtesy t Chemical Engineering. Klein's method requires that in the diy pressure drop equation, Eq. 6.42 , the vapor hole velocity uh is based on the area of holes on the deck of a valve tray Ado , and not on the slot area. In many valve trays, the orifice diameter is standardized at 1L 2 in. Values of Kc and K0...

## I

Distillation, King in separations, will remain m the workhorse separations device of the process industries. Even though it is old in art, with a relatively mature technology mpport base, it attracts research and afessional interest. Without question, sanation will sail into the future with dear skies and a strong wind. It will remain Ac key separation method against which mitcrnate methods must be judged. Distillation is the most important and most stable separation technology. The skyline of...

## Acknowledgments

Tbe author wishes to express his gratitude to Brown amp Hoot Braun, particularly to Walt Stupin and to Jim Gosnell, for their strong back-Bg and support for this effort. Special thanks are also due to my parents for their warm encouragement and inspiration throughout and far the German translations. The author is also grateful to his coauthors Joe Haas, David Hart, and David Gill for producing out-ttanding chapters while keeping ahead of all the deadlines. Appreciation is also due to my mentors...

## Tray Efficiency Scaleup

Prior to discussing scaleup, the factors that affect tray efficiency need to be addressed. These factors are addressed in Sees. 7.3.1 to 7.3.3. Considerations relevant to the effect of flow regime were previously discussed in Sees. 6.4.4 and 6.4.5. 7.3.1 Effect of errors In Vapor-Liquid Equilibrium VLE on efficiency Errors in relative volatility are the most underrated factor that affects both tray and packing efficiency. The effects are direct when VLE errors affect separation stage...

## Tray efficiency calculation example

Example 7.1 For the column in Examples 2.4 Sec. 2.3.1 , 3.4 Sec. 3.2.5 , ani 6.1 Sec. 6.5.2 , find the tray efficiency. solution The O'Connell correlation requires liquid viscosity and relative volatility at the average arithmetic temperature between the column top and bottom. From Table 6.10, the average temperature is 70 309 2 190 F.This temperature is closest to stage 8. Table 6.10 gives a liquid viscosity of 0.133 cP for this stage, and shows little variation in liquid viscosity throughout...

## Tray Efficiency Fundamentals

Overall column efficiency is defined by .V, is calculated by any of the methods in Chaps. 2 to 5. Once the tray efficiency is known, the number of actual trays can be obtained from Eq. 7.1 . Since efficiencies vary from one section to another, it is best 12 to apply Eq. 7.1 separately for each section e.g., rectifying and stripping . In practice, efficiency data and prediction methods are often too crude to give a good breakdown between the efficiencies of different sections, and Eq. 7.1 is...

## E3

Liquid product Figure 2.3 Continued and those below it are stripping Fig. 2.3c . In multifeed fractionators, the more precise functional criterion below is used to distinguish the rectifying from stripping sections. The stripping section has a net downflow of material. The vapor serves only as a recycle stream to remove lights from the liquid. Therefore, the quantity of liquid exceeds the quantity of vapor in the stripping section. The converse applies in the rectifying section, This section...

## N A

Where hc is calculated from the Hofhuis and Zuiderweg equation Eq. i.6.67 . A close inspection of the experimental data correlated 85 shows that this too is a gradual transition, which occurs over a range of values rather than at a sharp point. Valve trays. The amount of work reported thus far on valve tray regime transition is small and entirely based on air-water tests. Correlations proposed to date require the knowledge of liquid holdup at transition, which is generally not available, and...

## Examples Of Distillation

So, by returning reflux to the column at a constant rate, the mole fraction of benzene was increased to 0.84 in the receiver and decreased to 0.13 in the still pot. Remember, the simple still only concentrated the product to 0.58 mole fraction while reducing still concentration to 0.10 mole fraction. Other useful information can be developed by further consideration 1. Because the column has only a rectifying section, the concentration of the light component in the still can never be reduced to...

## Solving Equations Fractional Distillation Method -sndholm Naphtali

Where x, represents all of the variables of stage j and f, represents all of the functions of stagey. Because of this block form of the Jacobian, the computer time and storage is not great, possibly less than that required by a Tomich method. All of the global Newton methods have a sparse Jacobian matrix. About 95 percent of the matrix is zero's and it is quite simple to store only the nonzero elements. There are many numerical methods routines available specifically for solving sparse...

## Key Concepts of Multlcomponent Distillation

This topic is best illustrated using an example. The example used here is the depropanizer described by King 7 , which has previously been analyzed by Jenny 20 , Hengstebeck 21 , and Edmister 22 . Example 2.4 A material balance for the column is shown in Table 2.7. The column operates at a pressure of 315 psia. The feed is 66 percent vapor at the column inlet. The relative volatilities of the components at 205 F feed plate temperature are shown in Table 2.8. The column is equipped with a...

## Entrainment Correlation For Sieve Plate

Figure 6.1 Fair's entrainment correlation. J. Ft. Fair, Petrol Chem Engr. 33 JO , p. 45,1961, reprinted courtesy of Petroleum. Engineer International, Dallas, Texas. Figure 6.1 Fair's entrainment correlation. J. Ft. Fair, Petrol Chem Engr. 33 JO , p. 45,1961, reprinted courtesy of Petroleum. Engineer International, Dallas, Texas. dependently by the extensive data analysis of Koziol and Mackowiak 55c . In the froth regime, the Kister and Haas correlation does not apply, and Fair's correlation...

## Cc

M-1 H M Weir Lenglh Figure 6.15 Plots of entrainment versus liquid flow rate featuring entrainment minima. H. Z. Kister and J. R. Haas, I. Chem. E. Symp. Ser. 104, p. A483, 1987, reprinted courtesy of the Institution of Chemical Engineers, UK. Es 4.742 10 V lM x 10 V gt 6.27 The clear liquid height at the froth-to-spray transition, hct, is calculated using the Jeronimo and Sawistowski 35 correlation, as modified for physical properties by Kister and Haas 36 ....

## Effect Of Tray Spacing

Kister, Distillation Operation, Copyright 1990 by McGraw-Hill Inc. Reprinted by permission. Low tray spacing also enhances the tendency of all types of flooding other than downcomer choke flooding. As tray spacing diminishes, drops have to travel a shorter distance to be entrained spray entrain-ment flooding , the froth envelope becomes closer to the tray above froth entrainment flooding , and a lower downcomer backup is sufficient to cause flooding. Tray spacing has little...

## Sieve Tray Design

Not generally suitable for operation under variable loads About 4-5 1. Some special designs achieve or claim 10 1 or more Excellent, better than valve trays. Good at extremely low liquid rates Low, even lower than sieve trays 10 . Unsuitable for variable load operation High, about 3 times higher than sieve trays 4 Moderate. Early designs somewhat higher. Recent designs same as sieve trays About 20 percent higher than sieve trays 11 High. About 2-3 times the cost of sieve trays 10,11...

## Willie Chan Aspentech

Grens, Am. Inst. Chem, Engrs. J., 20, p. 238, 1974. 58. Rafal, M., S. J. Sanders, and R. D. Young, Paper presented at AlChE National Meeting, Washington, D.C., November, 1988. 59. Bondy, R. W., Paper presented at AIChE National Meeting, Chicago, 111., November, 1990. 60. Rose, A., R. F. Sweeny, and V. N, Schrodt, Ind. Eng. Chem., 50, p. 737, 1958. 61. Jelinek, J., V. Hlavacek, and M. Kubicek, Chem. Eng. Sei., 28, p. 1825, 1973. 62. Mori, H., I. Yamada, T. Tsuiki,...

## Downcomer Apron

The f-factor is the square root of the kinetic energy of the vapor. The velocity in Eq. 6.2 is usually but not always based either on the bubbling area Aq or on the net area A . The user must beware of any data for which the area basis is not clearly defined. In some cases, the hole F-factor, Fh, is used. This parameter is based on the hole velocity, uh, and is given by A term even more suitable for describing vapor loads than the f-factor is the C-factor, CS defined as The C-factor is related...

## A

Inicrccpi of component balance line on the y-axis - S Fk D zk .' ---yrr- 2.40 The foregoing equations can be directly applied to a column having several feeds and no side-products. They Vj V ., q - 1 Fj., 2.45 A simple column can be regarded as a two-section complex column. Section 1 is the rectifying section, while section 2 is the stripping section. Table 2.6 draws an analogy between the simple and the complex table 2.5 Equations Applying to Each Section J of a Complex Fractionator Continued...

## Rigorous Distillation Calculations

Before the 1950s, column calculations were performed by hand. Although rigorous calculation procedures were available, they were difficult to apply for all but very small columns. Shortcut methods were therefore the primary design tool. Rigorous procedures were only used for small columns or for final design checks. Inaccuracies and uncertainties in the shortcut procedures were usually accommodated by overdesign. The introduction of computers has entirely reversed the design procedure. Rigorous...

## Murphree Plate Efficiency Graph

Using Eqs. 2.11 and 2.16 , Eq. 2.9 for the rectifying section component balance line can be expressed in terms of the reflux ratio As the reflux ratio decreases, so does the slope of the upper component balance line. The effect of reflux ratio on the component balance lines is illustrated in Fig. 2.11, using the benzene-toluene system in Example 2.1. Any practical separation requires that the component balance lines intersect below the equilibrium curve, as for a reflux ratio of 3.0 in Fig....

## Fractionating Still

Thus, even when starting with the relatively dilute concentration of 5 mole percent benzene, 60 percent of the mixture has to be boiled off in order to reduce the residual benzene concentration to 1 mole percent. Furthermore, the concentration of the recovered benzene is not a dramatic improvement over the starting mixture. As shown by the two examples above, simple distillation produces only poor separations, with either high or low concentrations of the light component, even with large energy...

## Examples Of Mislocated Feeds

Distillation do not occur at the feed points, as they do in binary distillation, but above and below the feed points. The stages between the lower pinch zone and the feed point fractionate the light nonkeys from the bottom section liquid, and those between the upper pinch zone and the feed fractionate the heavy nonkeys from the rectifying section liquid. Due to the presence of nonkeys near the feed, determination of the best feed point in multicomponent distillation is difficult. King 7...

## How To Find Optimum Reflux Ratio

Figure 3.4 Reflux rate optimization for an existing column. Reprinted by permission. Copyright Instrument Society of America, 1978, from P. R, Latour, Instrumentation Technology, July 1978. only. For simplicity, the reflux rate can be used instead of S. Further, since the column is existing, there is no capital cost, and all the costs involved are utility costs. Therefore, the total costs curve becomes the utility costs curve. The net variable value is the difference between the recovery value...

## Effect Of Temperature On Relative Volatility

The most important term in the equations both for f-values and relative volatility is the vapor pressure term. Effect of temperature or pressure. This effect can be illustrated with the aid of a Cox chart Fig. 1.2a . This chart shows a steep increase of vapor pressure with temperature. For this reason, the Jf-value for each component increases steeply with temperature. The Cox chart also shows that in general, for members of a homologous series, vapor pressure of the less-volatile component...

## V

Vap Vap A B Vap Vap A B Figure 2.2 Ideal and nonideal stages in distillation systems, a , 6 Thermosiphon reboiler arrangements c , Id fractionation tray arrangements e , if inter-condenser arrangements. Arrangements gt , d , and f are ideal stages. Arrangements a , c , and e are n on ideal stages. vapor-liquid contact, equilibrium will be established. Criterion 3 will be satisfied, making arrangement 2.2d an ideal stage. Figure 2.2e and f shows intercondenser arrangements. The system in Fig....

## Hengstebeck Diagrams

Chapter 1. introduction to Distillation 1 1.1.1 What Is Distillation 2 1.1.2 Why Distillation 2 Vapor-Uquid Equilibrium VLS 3 1.2.1 K-Value and Relative Volatility 3 1.2.2 Ideal and Non-Ideal Systems 6 1.2.3 Effect of Temperature, Pressure and Composition on K-Values 1.2.5 Calculation of Bubble Points and Dew Points 13 OHpter2. Key Fractionation Concepts 19 2.1.1 ideal and Nonideal Stages 20 2.1.2 Stripping, Rectification, and Fractionation 23 2.1.3 Material and Energy Balances 25 2-2 x-y...