Tmm

Umn, or the auxiliary equipment, being under- or oversized, the feedstream being poorly located because the presence of certain components were not anticipated. mistaken calculations, wrong assumptions about the efficiency of cer- j tain elements, or poor control logic. Mechanical-design mistakes can result in such problems as nozzles located improperly with respect to packed-column distributors or tray downcomers, and the early failure of internals because the wrong material was selected (See...

Solution

(i) Since steam is available at 15 psig, it can be condensed at and ' up to 250 F. The bottom stream is 90 percent pure toluene (ii)j (Example 2.1) with an atmospheric boiling point of 223 F. To ensure a minimum of 20 F approach across the reboiler, the HP column can be operated at a pressure close to 1 atmosphere, perhaps slightly higher (bottom temperature cannot exceed 23 0 F). For simplicity, assume the HP column is atmospheric. The HP column produces 95 percent pure benzene as distillate...

Suggested Further Readings

I Null, H.R., Heat Puttds in Distillation, Chen. Enc. roc., _2 58, 1976. Stephenson, R.M. and T.F. Anderson, Energy Conservation in Distillation, Chem. Eng. Prog., 76. 68, 1980. Null, H.R., Keat Pumps Reduce Distillation Energy Requirements, Oil & Gas J., Februarv 9, p.96, 1976. O'Brien, N.G., Reducing Column Steam Consumption, Chem. Enc. rcg., 72 (7), 65, 1976.

Rt

-x, In (x, + AiiXi) - x, In (xt + A,,X ) A . A In in - In (x, + A.,x,) + x, ( ) In y, -ln(x, + AltXi)- Xi ( r----. ) -4,11. C RT In y, (A +311 + 5i.')xt* 4(B+4C)x,*4 l2i.V RT In y, (A - SB + 5i.)x,' + 4< B - 4i.)x,' + I2(V (Reid, R.C., el a ., The Propertior of t'.ases and Liquids, 1977, by courtesy, McGraw-llill Book Company.) l' T 0 + t C,. RT 1 * x. + x,i * + x,G )

Ri Rt

R and f are pure-component parameters and coordination number 1 10 ft jj('.- )-('.-I> ft - .)-(',-I) Relcrence 66 diKiinrs the MarRulcs, van l.aar, Wilson, and NRTL equation*. The (INIQIIAC equation n discussed in Rel. S. 'Two-suffix signifies that the expansion (or g' is quadratic in mole fraction. Tliirc-sufl.ix signifies a third-oidcr, and loiir-sullix signifies a fourth-order equation. 'NRTL* Non Random Two liquid. ' Kit ** - Ktfl A 'UNIQUAC- Universal Quasi rheinical. Parameters 4 and r...

Product

THEORY Thermodynamically, the heat pump can be described as a heat-engine in which the following processes take place (Figure 4.5) (i) Overheads from the column is compressed, path A3 on Figure 4.9. (ii) The compressed overheads is cooled and condensed at the column rebciler, path BC on Figure 4.9. (iii) The condensed overheads is expanded across the reflux control valve, path CD on Figure 4.9. (iv) The liquid is boiled and converted into vapor by the column action, path DA on Figure 4.9. Work...

Pr025y002300

R 16v*e 12.17.1 Lnn Oil Still with Ptod - Bottom Interchangor INSTALLATION. An olefins plant debutanizer, which separates butadiene and butenes as the top product from pyrolysis gasoline tha-_ i leaves in the column bottoms. The bottom product flowed to a j hydrogenation reactor after being preheated by reactor effluent in ' the reactor feed-effluent exchanger (Figure 12.18.1). The column received two feeds. The smaller feed stream, which entered at a higher point up the column, contained most...

Os

EffCCT Of EiJUM6 D DOWNCOftGA VOU ne INSTALLATION An olefins plant heat-pumped front-end deprcpanizer (Figure 12.2.1). Top section diameter was about twice as large as bottom section. Feed was mostly vapor, but some liquid was condensed in the feed chiller. PROBLEM The column was unstable, and both pressure drop and bottom level fluctuated periodically. The period of fluctuation was about 30 seconds. Amplitude of fluctuation significantly increased as plant rates were raised....

Oa

FIGURE 9.3 CfiPfiClTy COMPARISON OF irr ' PACKING BND SIEVE TRP S & P,SED ON STRlGlc SOLAN (s, ii) FIGURE 9.3 CfiPfiClTy COMPARISON OF irr ' PACKING BND SIEVE TRP S & P,SED ON STRlGlc SOLAN (s, ii) I EFFICIENCY COMPARISON The efficiency of packings and trays is j compared in Figure 9.4. This comparison is even less reliable thar. that in Figure 9.3. While the curves for trays are exact, these for 1 the packings are based or. the rules of thumb by Porter and Jenkins (4) and Frank (5) for...

Nomenclature

EBP Effective boiling point (Equation 1.13), R Fe Correction factor in convergence pressure prediction, Figure 1.13 Ge Gibbs excess free energy, Btu gE Molar Gibbs excess free energy, Btu lb mole K K-value (defined in Section 1.1.1) R Gas law constant, Btu (lb mole) (*R) 4 Poynting pressure correction term

Mpr1l1122

UNIQUAC (UNified QUAzi Chemical) This model assumes that the excess free energy is the sum of two contributions, one accounting for the size and shape effects (combinational), the other accounting for molecular interactions (residual). It resembles the Wilson equation, but the composition variable is surface area fraction i instead of mole fraction. The equation was first developed by Abrams I land Prausnitz (44) and later modified by Prausnitz et al (45) . It j uses two adjustable parameters,...

Mpr1l11

Some laboratories that carry out industrial VLE data measurements are listed below. Some of the addresses may not be fully up-to-date. 1 Dr Gran- M Wilson Wiltec Research Co, Inc 488 South 500 Street West Provo, Utah 84601 2 Dr James M Berryman P-V-T, Inc Chemical Engineering Department William Marsh Rice University P 0 Box 1892 Houston, Texas 77001 D B Robinson & Associates Edmonton, Alberta, Canada Chemical Engineering Department Washington University St Louis, Missouri Chemical...

Mixed

FIGURE 8.3.4B CASE STUDY NO.4 (SftSED ON REF 10) POSTMORTEM The improvement resulted from two factors. I 1 The analyzer provided a direct measurement of the water profile, and took action before water contaminated the bottom product, or trays were dried out. 2 The reboil rate was greatly reduced and water concentration was maintained at all times at a minimum level sufficient to form an azeotrope. Following the modification, it was found that sufficient water was always present, and that live...

M

Condenser end refaoiler duliei, million Blu li Condenser end refaoiler duliei, million Blu li The economic curves on Figure 4.4 show that with the lighter feed, an all vapor feed was optimum with the heavier feed, 0-40 percent vaporization vas the optimum. Perhaps a general guideline that can be inferred from Patterson and Wells' analysis is that the optimum fraction of feed vaporized increases with the concentration of lights Application of feed preheating (or increasing the feed vapor...

Lll

Many problems with the auxiliary-equipment by comparing the actual state of critical variables against values for design, or normal, operating conditions (for example, the ratios of steam rate or reflux rate to feedrate) and noting signs of control limitations (such as a wide open control valve). Reboilers are generally classified as natural or forced circulation. The first includes vertical and horizontal thermosiphon types, kettle reboilers. and internal tube bundles (Figure 2). In these...

L

INSTALLATION A total air condenser condensing column overhead. Condenser length was 32 feet and the tubes were sloped 5-6 feet. Condensate was backed up from the accumulator drum to ensure there was a liquid level inside the tubes. This level varied according to the capacity requirements. Column pressure was controlled by a control valve in the line from the column to the condenser (Figure 8.2.4). PROBLEM A liquid hammer that shook the whole unit occurred during startup. CAUSE Under some...

Ki Xi

The dew point of a mixture is calculated from The calculation method is as follows (at constant pressure) (iii) Obtain Ki xi for bubble-point calculation. If smaller than unity, increase temperature. If greater than unity, decrease temperature. Repeat steps (ii) and (iii) until converged. Alternatively obtain Yi Ki for dew-point calculation. If smaller than unity, decrease temperature. If greater than unity, increase temperature. Repeat steps (ii) and (iii) until converged.

J

Figure 4.7 compares a two-stage condensation arrangement to a conventional system. In a 2-stage condensation system, only reflux is condensed in the first stage. This makes the reflux to the column heavier, and reduces the recycle of lights around the reflux loop. The lower recycle of lights for the same condensation rate enables recovery of the reflux condensation energy at a higher temperature. When the product is mostly liquid, vapor composition leaving the reflux drum is similar to the...

Jbb

In general terms, at the low reflux rates the column was operated as a gasoline-LPG separator instead.of an absorption oil-gasoline LPG separator. This lowered temperatures throughout. However, the column was over-reboiled this returned the bottom and top temperatures to their design values. This is explained in detail J At the low reflux ratio, a substantial fraction of the gasoline j reached the bottom. This would have caused a lower temperature at the base of the column, but the control...

Isolvent

PlGUREf 12.11.1 SOLVENT RECOVHRy COLUHN CASE STUDY NO. 12 (Contributed by F. Wetherill, Santa Fe Braun Inc., Alhambra, Calif) INSTALLATION A specialty chemical plant producing a heavy, water soluble alcohol. Effluent from a front-end hydrogenation reactor was purified into the desired product in a four column separation plant, shown as the heavy lines on Figure 12.12.1. The first two columns separated water from the feed. Final traces of water were removed in the flash drum overheads. The...

Info

1.2.3 Computer K-Value Prediction Methods for Hydrocarbon-Type Systems I (i) The Redlich and Kwong equation for the vapor phase (ii) An empirical expression based on the generalized j corresponding states PVT correlation of Pitzer el al (26) I for the liquid phase fugacity coefficent. j (iii) The Scatchard-Hildebrand (solubility parameter) for liquid j I (iv) Empirical mixing rules, based on pseudo-critical (v) The Poynting correction is neglected. j The advantages of this method are (i)...

Wsv

1 INSTALLATION A Benfield Process hot pot absorber. The absorber 1 uses hot pc.assium carbonate solution to absorb C0a and K2S from concentrated sour gas (Figure 12.9.1). Because of the corrosive environment, the column was packed with 2 inch polypropylene Raschig rings. HISTORY The absorber plugged on start-up. It was losing capacity during the first couple of days, until it was virtually plugged. When it was opened up, the plant observed that the plastic rings had melted, thus plugging the...

Wqr

I 3 0 Rathore, R N S, Chem Eng, June 14, p 155, 1982. 31 Galstaun, L S, W S Chaffin, M K Dunlap, B M Neeper, and K H Wang, Oil and Gas Journal, Nov 12, p 223 , 1979 . 32 Finlet, S, Hydroc Proc _58 (2), 95, 1979. j 33 O'Brien, N G, Chem Eng Prog 72 (7), 65, 1976. 3 4 Tyreus, B D, and W L Luvben, Hydroc Proc, (7), 93, 1975. i 3 5 Abrahams, H, I Chem E Symp Ser 54, p 1, London, 1978. 3 6 Rush, FE, I Chem E Symp Ser 56, p 4.1 1, London, 19 79. j 37 Danziger, R, and W Baumer, I Chem E Svmo Ser 56, o...

Vxm

FlGURE S.2.1 condenser ARRANGEMENT, CASE 1 (based on REF 2 ) CASE 2 Improper Draining (Reference 2) INSTALLATION A horizontal in-tube condenser with axial inlets and outlets (Figure 8.2.2). PROBLEM Condenser could not achieve its design capacity. Problem occurred because condensate from the axial outlet could not drain, so about half the area was inactive. SOLUTION Ensure drains are placed at the lowest part of the exchangers, and vents are placed at the highest part. figure 8.2.2 cortden&...

Qos

INSTALLATION A 10-foot ID caustic wash tower (Figure 12.16.1) which removes a small quantity of C0_ and traces of H-S from light j hydrocarbon gases at about 200-300 psig. The tower contains 40 single pass valve trays at 24 inch tray spacing. Each tray is equipped with a 6 inch wide downcomer. Overheads from the column flows via a knockout drum to a compressor. The plant was at its initial startup. PROBLEM At low plant rates the column operated well. As rates were increased to 60-70 percent of...

Oki

The ratio W Q_ is a measure of the potential cf applying the heat pump technique to a g-iven system. A high ratio indicates that a large amount cf compression work is required to achieve the required refcoiler duty, and that a heat pump is unlikely to be eccr.crr.ical. A low ratio implies the converse. Equation 4-1 states that this ra ic is directly dependent on the temperature difference between zhe column bottom and column overhead. Equation (4-1) can be written in terms of pressure instead...

Nal

In the course of the comparison, several assumptions regarding tray j geometry, type of system, column design and safety margins needed to be made. These assumptions, as well as the procedure used to obtain the curves shown on Figure 9.3, are spelled out and discussed in Appendix 9A. Should the user wish to use this chart for any purpose other than drawing general guidelines such as those described below, he is strongly encouraged to derive a diagram similar to Figure 9.3, using the procedure...

Eyt

41 Shaner, R L, Chem Eng Prog T4 (5), 47, 1978. 4 2 Tyreus, B D, and W L Luvben, Chem Eng Prog 72 (9), 59, 1976. 4 3 Kina, C J, D W Gantz, and F J Barnes, Ind Eng Chem Proc Des Dev _U (2), 271, 1972. 44 King, C J, Separation Processes, 2nd Edition, McGraw-Hill, New York, 19 80. 4 5 Benedict, M, and T H Picrford, Nuclear Chemical Engineering, .McGraw-Hill, New York, 1957. 4 6 Stupin, W J, and F J Lockhart, Chem Eng Prog _68 (10), 71, 19' 47 Stur in, W J, PhD Thesis, University of Southern...

Atp

The azeotrope separation scheme (Figure 4.10f) is a variation of the backward feed arrangement suitable for azeotrope separation, and is illustrated with reference to a process for purifying ethanol (39). In this case, the azeotrope increases in alcohol content as pressure is reduced. The HP column operates at atmospheric pressure, and produces 92 mol percent ethanol in the overheads, while the LP column operates at 95 mm Hg and produces 95 percent ethanol in the overheads. Note however, that...

1

Eng., 12_ (7), 5, 1971. 10. Lenoir, J.M., Paper presented at the A.I.Ch.E. meeting in Anahein, Calif., June, 1982. i 11. Newnan, S.A., Pacer presented at the A.I.Ch.E. meeting ir. 3oston, j Ma., August, 1979. j 12. Chac K.C. and G.D. Seader, A.I.Ch.E. J., 598, 1961. j 13. Grayson, H.G. And C.W. Streed, Paper 20-P07, Sixth World Petroleum Conference, Frankfurt, June, 1963. 14. Reid, R.C. and T.K. Sherwood, Properties of Gases and Liquids, J 2nd Ed., McGraw-Hill, 1966. 15....

H

Eat exchangers, vacuum pumps or ejectors, process pumps and instrumentation represent some of the critical components of distillation columns (Figure 1). Often, the problems of the column and its auxiliary equipment are inseparable. A problem with one item of the auxiliary equipment can impose a limit on a column's capacity or separation ability, or both. For example, an undersized reflux valve may constrain the reflux rate, or a fouled reboiler may-suppress column boilup. A problem with any of...

Figure

INSTALLATION An olefins plant C, splitter (Figure 12.19.1). Feed to the column was a vapor ethylene ethane mixture with minor quantities of other components. Top product was polymer-grace j ethylene, wnile bottom product was ethane, which was recycled to the j plant's cracking furnaces as a cracking feedstock. The main requirement of the column was to produce on-spec ethylene. There was an economic incentive to minimize the amount of ethylene in the column bottom stream, but in this case the...

Figure 12162 Downpipes Rdded To Increase

Hower Jr., Santa Fe Braun Inc., Ainambra, Ca.) INSTALLATION A lean oil still in an absorption-refrigeration gas jplant (Figure 12.17.1). Feed to the still is rich absorption oil, containing gasolines and some LPG absorbed from the natural gas. Lean oil leaves as the still bottom product, while gasolines and LPG are the top product. The still was reboiled by a fired heater, and reflux was supplied by an air condenser. Top temperature was about 175 F, bottom temperature 520...

Figure 12131

INSTALLATION A whisky still equipped with bubble-cap trays. Liquid j flow rates are extremely low, about 2 to 3 gallons per hour per foot of weir. Excessive reflux is to be avoided, as this gives excessive washing and detracts from the product quality. PROBLEM The still had significant entrainment and weeping problems. This affected the quality of the whisky. INVESTIGATION Glass side-ports were installed to enable visual observations. These showed weepage between the risers and the plate, and...

E

Where G- is trie observed excess free energy of a mixture, above What i it would oe for an ideal solution at the same temperature, pressure I and composition. i Each model for liquid activity coefficients correlates the excess free j energy to composition by its own expression. All these expressions contain adjustable constants which, at least in principle, depend on temperature. This temperature dependence may sometimes be neglected, especially if the temperature interval is small. j The...

Case Study No

J INSTALLATION An aldehyde column, flooding at rates well below i design. ANALYSIS Gamma scans showed that the column flooding started in the section just below the feed tray and progressed up the column. A more detailed scan across a flooded tray as well as the downcomer was carried out (Figure 12.1.1). The presence of a second inflection j point is interpreted as foaming in the downcomer. I CURE Initially, an antifoam agent was injected, which substantially increased capacity. Continuous...

Other Revamp Techniques

ADDING COLUMN SECTION IN SERIES Adding a section to the column in series is simply a means of increasing the number of trays. The new section may be added either directly to the existing column, or as a separate column in series with the existing column. Adding a new section at the top of an existing column is usually preferred, unless there is a height limitation or the added section is large. Care must be taken to ensure the feed enters the modified column in the right location. This...

Figure 835 case stuoy tfo

( flS6D OKJ REF ) CONDENSATE TEMPERATURE CONTROL CASE STUDY No. 6 Hot Vapor Bypass Problem INSTALLATION A hydrocarbon column equipped with a submerged condenser and an elevated reflux drum (Figure 8.3.6). The control j system in similar to that shown in Figure 17.5D in Reference 12. j PROBLEM Pressure fluctuations and inability to keep column pressure constant. ANALYSIS The cause was diagnosed to be mixing of liquid, which left the condenser subcooled, with vapor. Collapse of vapor took place...

Uaw

I (ii) The number of stages available in the bottom section is 7 ( 14 x 50 percent). By trial and error, an operating line that will give 7 stages in the bottom section can be found. This operating line is shown on Figure 4.2(a). Slope of this operating line is 2.0. Above the interreboiler, the L V ratio is the same.as that in Example 2.1, ie L' V* 363 234 1.55 (Figure 2.15). Let the quantity of liquid vaporized in the interreboiler be AV, then Solving gives V V' 0.45, or 45 percent of the...

A

Trapped noneondensable gas lowers heat transfer baffles can let coolant bypass of por tions of the tube bundle, reducing the coolant flow through the tubes and the effective temperature difference for condensing. Common causes of exces- sive clearance include corrosion, ero, j sion. and bowed tubesheets. The last i can be caused by excessive pressure oc. a thermally-induced tube contraction which can occur in a condenser having an inadequate shell expansion joint or one that is...

And Packings

Based OH RULES OF THUH 6 PORTER fl 4D JENKINJ ( ) AN FRANK (sj I 3est results for replacing trays with packings are obtained at lev I values cf flow parameters, i.e. low liquid loads and low vapor densities, such as those experienced ir. vacuum and atmospheric pressures, particularly if the trays operate at a relatively low ' efficiency (Figure 9.3 and 9.4). Another case where replac-r.g trays with packings is effective is systems which tend to foam 'section .5.1), as packings can handle these...

Random Packings

OBJECTIVES In order to compare the capacity of structured packings to the capacity of trays and random packings, a chart, such as Figure 9.5 can be used. The construction of such a chart requires that several assumptions are made. The assumptions made in developing Figure 9.5 may be a poor approximation for many applications, and this diagram is therefore only suitable for defining very general guidelines. The user is therefore strongly encouraged to develop his own chart, similar to Figure 9.5...

Column Startup

France, Giitscn, inc. Distillation-column troubleshooting' begins with the recognition that the expected separation or capacity is not being delivered, and ends with action that restores performance. The tasks of the troubleshooter are first, to identify the problem next, to determine its cause and lastly, to recommend a remedy. Because the economic loss from reduced column performance or extended downtime can be significant, the pressure to restore column...

Estimating Separation Efficiency Part 2 Vital Grossel Olsen

Pract al Tips on Tower . fee. 7. 1987. pp. 101- AIChE. Trav Distillation Columns. AIChE Equipment testing Procedure.' America.-. Inst, of Chem. Engrs New York. 19 , . 2. Anderson. A. E and Jubin. J. C Case Histories of the Distillation Practioner. Chew. Eng. Prog October 1964. pp. tiO-63. 3. Bolles. W. L Estimating Valve Tray Performance. Chem. Eng. Prog September 1976. pp. 43-49. 4. Jamison. R. H Internal Design Techniques. Chem. Eng. Prog March 196 . pp. 46-51. 5. Kister. H. Z Design and...

Non Condensibles Beer Column

Vertical Thermosiphon Reboiler

FIGURE 8.1.18 TEfifERftTUftE CyCLE , CASE 1 CASE STUDY No. 2 Heavies in Inlet Line Reference 2 author had similar experience . INSTALLATION A vertical thermosyphon reboiler, processing a mixture of two components - a high boiler and a low boiler Figure 8.1.2 . PROBLEM Heat transfer and circulation rate deteriorated with time. Neither fouling nor composition variations appeared to be the cause. The problem was diagnosed to a lack of outlet for residue. It accumulated at the base of the reboiler...

Even if a multicomponent system falls outside the methods normal limits it may be possible to get useful vaporliquid

Wilcox, Jacobs Engineering Group, Inc. The UNIFAC group-contribution method outlined in the preceeding article is a means of calculating multi-component vapor-liquid equilibrium VLE data. Experimental data are always preferred, but UNIFAC can prove useful if they are unavailable, or if they are available only for binary mixtures and not the multicomponent ones of interest. There are, however, limits on where UNIFAC can be applied Pressure no more than a few i.e., 3 4 atmospheres All...

High Flux Tubes Condenser Overhead Distillation Column

Substituting the above in equation 4-1 gives Equation 4-2 shows that the ratio W QR can be expressed I the log of the pressure ratio. iEither the temperature difference, or the pressure ratio, can be used to measure the potential of applying the heat pump technique. Compared to the relationship in equation 4-1, the relationship of equation 4-2 is more complex and more difficult to express in terms I of readily available parameters such as column top and bottom temperatures for this reason, the...

Trouble Shooting Distillation Columns

Cross Flow Single Pass Sieve Tray

France, Glitsch. Inc. ' For information about the authors, see p. 123 of the first article o this series. .Marc 19S9. p. 116. Overall, trayed columns operate via countercurrent liquid and vapor flow, with staged contacting for heat and mass transfer. Each stage is often modeled as a mixer-separator, with liquid-vapor contacting followed by the separation of liquid and vapor for transport to, respectively, the stages below and above Figure 1 . This description...

Vapor Blanketing Reboiler Corrective Actions

Evaporation Pracitcal

Product that crystallized during the shutdown of a distillation column decorate the fouled finned tubes of a reboiter steam-condensate-seal blowing, film boiling, heating-medium inadequacy, boiling-point elevating, foaming, inert blanketing, leaking and undersizing. Fouling The vaporization of process fluids at tube walls can precipitate dissolved solids onto the tubes. Tar-like materials in the feed may plate out on metal surfaces. Tube-wall temperatures which are higher than bulk-fluid...

Columns

Liquid Holdup Trays Distillation Column

The first step identifying the problem will usually be simpler if column performance has suddenly deteriorated than if capacity or efficiency declined gradually. Except when related to auxiliary equipment or instrumentation, most distillation problems arise from flooding impeded liquid flowpath , excessive pressure drop impeded vapor flowpath , or inefficiency insufficient liquid and vapor contact . Of course, these problems do not usually occur independently. After attempts to stabilize column...

Internal Hardware Revamps

Distillation Dual Tray

WHEN EFFECTIVE A quick browse through Sections 5.2.3 and 6.3.4, which list factors affecting capacity and efficiency, can define the effectiveness of this technique. Changing layout may be used effectively to increase column capacity, but the technique is rather limited in its ability to significantly improve column efficiency. It is thus suitable for capacity revamps only. METHODS The methods commonly used depend on the flooding mechanism which restricts capacity, and can simply be deduced...

Bc

Demethanizer

Figure 4 ko thermal coupling BRuc-na's scheme Figure 4 ko thermal coupling BRuc-na's scheme FIGURE 4.12 RNRL TICflL DiftGftAM 0F THE 4.2.9 Other Common Heat Integrations DIFFERENT COLUMNS One of the most straight-forward energy saving schemes is thdt of direct heat integration between different columns. Such a scheme can be implemented whenever one column rejects energy at a temperature sufficiently high to be utilized for heatir.c in another column. Figure 4.13 shows a typical example. Energy...

Comparing The Capacity Of Trays And Packings

OBJECTIVES In order to compare the capacity of trays and packings, a chart such as Figure 9.3 can be used. The construction of such a chart requires that several assumptions are made. The assumptions made in developing Figure 9.3 may be a poor approximation for many applications, and this diagram is therefore only suitable for defining very general guidelines. The user is therefore strongly encouraged to develop his own chart, similar to Figure 9.3, whenever an alternative set of assumptions...

What Is Distilation And Show In Practical

Mole Fraction And Distillation

While the overhead product consists of a mixture of spent C4s butanes, butenes, butadienes that passed through the reaction step as inerts. The overhead composition depends on the composition of the feedstock, which is generally a C4 cut from a catalytic cracker or steam cracker. C2B, one of the heavier C4s, is characteristic of the overhead stream. The other system is diethanolamine DEA and trietha-nolamine TEA . Ethanolamines, including monoethanol-amine MEA , are used to scrub sour acid...

Cf

The group-contribution methods consider a liquid mixture to be a mixture of functional groups, rather than a mixture of molecules. Table I lists the groups currently included in the UNIFAC model. The properties of a mixture, then, are determined by the properties of the groups rather than of the molecules. This is like scaleup to molecules from smaller elements. For example, the mixture of dimethyl ether CHsOCHs and benzene QHe can be considered a mixture of CHS, CHsO and aromatic CH groups....

P s IT y

Pall Ring Capacity Parameter Graph

Figure 9.3 indicates that at this flow parameter, 1 IMTP is the most likely choice. This will be used as a first Capacity Factor of sieve trays at 18 inch tray spacing Capacity Factor of 1-inch IMTP 0.22 Figure 9.3 STEP 2 Mccify the above capacity factors as per Appendix 9A. 1 Correct sieve tray capacity factor for the smaller tray spacing. From Figure 5.10, this correction for the capacity factor is roughly at a flow parameter of 0.16 0.21 0.23 0.91 2 Allow a greater safety factor for the...

References

1 Davies, J A, Chem Eng Prog 61 9 , 74, 1965 2 Gilmour, C H, Chem Eng, June 19, p 221, 1967 3 Moore, J A in Rubin, F L Chairman and P Minton, Heat Exchangers That Did Not Work, Panel Discussion, AIChE Meeting, June 6-10, 1982 4 Bell, K J in Rubin, F L Chairman and P Minton Heat Exchangers That Did Not Work, Panel Discussion, AIChE Meeting, 5 Bell, K J, Chem Eng Prog 79 7 , 54, 1983 6 Kister, H Z, and T C Hower, Plant Operations Prog 6 3 , 151, 1987 7 Steinmeyer, D E and Mueller A C, Chem Eng...

Charts

Blood Pressure Nomogram

No 1 16 Nomogram for predicting equilibrium ratios of hydrocarbons in the low-pressure range. From Cajander el al., J. Chem. Eng. Data, 5 25 I960 . Reproduced by permission of C. F. Broun and Company. M. Van Winkle, Distillation, 1967, by courtesy, McGraw-Hill Book Company.

Appendix 9a Appendix 9b References

9.1 REVAMP TECHNIQUES 9.1.1 Objectives of Revamp Some of the common reasons for revamps are ii Reducing reflux and reboil - energy savings. j iii Accomodating new process conditions - new product 1 specifications, new feed composition. iv Reducing bottom pressure vacuum applications - decreasing j polymerization. TYPES For the purpose of discussion, most revamp objectives can be classified into three types A Capacity revamps - the objective of this type of revamp is to increase unit throughput....

Energy Saving In Distillation

Interreboiler

J 4.1.1 Classification of Energy Saving Techniques j Energy saving techniques can be classified into two categories 1 Techniques that involve a considerable amount of capital i expenditure. These techniques are generally capable of achieving large energy savings, and are mainly suitable for new i plants or major revamps. j 2 Techniques that involve a relatively small amount of capital i expenditure. These techniques generally but not always are capable of achieving smaller savings than those...

A A 1 A

Distillation Overhead Compressor

This exchanger superheats the column overhead while subcooling the reflux. Subcooling the reflux reduces the vapor flash generated upon expansion of the reflux stream. The lower vapor flash reduces vapor recycle through the compressor and therefore lowers compressor power consumption. This power reduction is somewhat offset by the higher compressor suction temperature and lower suction pressure because of exchanger pressure drop . The higher compressor...

Pr026h002000

Reformer General Arrangement

iv Trim condenser or trim reboiler are often used because the condensing and boiling- duties of- the column are net perfectly matched. These devices are also very helpful for startup. A trim condenser is more common when the product is withdrawn as liquid, while a trim reboiler is more common when the product is withdrawn as vapor, but other factors such as presence of a discharge cooler and the feed conditions are also important in determining which one of these if any is needed. v Discharge...

Spillover Distillation

Pumparound

One means of generating such a low-grade heating medium is by I applying the hot liquid belt technique. The equipment that is j usually needed is heat exchangers, a drum, a pump, and a heat j transfer liquid suitable for the temperature range of up to about ' j 200 F. Ideally, this liquid should be non-fouling, non-corrosive, I not excessively viscous and non-toxic. Cooling water is rarely suitable, because it tends to cause accelerated fouling at i temperatures greater than about 150 F, but...

Energy Saving Operation

Reflux and reboil rates are adjusted to produce or.-spec products. Product impuriry levels well below their specifications represent overrefluxing and cverreboiling, and waste energy. Operators tend to overreflux in the interest of smooth operation, and in order to maintain safe margin in case of upset. To minimize joverrefluxing, plant supervision must provide the operators with the jappropriate tools and incentives. These include INSTRUMENTATION Overrefluxing tends to be a greater problem in...

SE On REf a

Deethanizer Processes

8.3 Control Systems That Did Not Work CASE STUDY No. 1 Analyzer Located in the Next Column Product Line INSTALLATION An absorption-refrigeration gas plant. Rich absorption oil contained absorbed hydrocarbons from C_ to gasoline. In order to regenerate the absorption oil, the deethanizer stripped out the C. and C2 hydrocarbons. Gasolines, LPG C.-C. , and C, impurities from the bottom of the deethanizer were recovered ifl the still overhead product Figure 8.3.1A . There was an economic incentive...

Lp

Distillate Stream

FIGURE 4.10 hi iTi-EFFECT i TllLftTION continued FIGURE 4.10 hi iTi-EFFECT i TllLftTION continued In the forward-feed arrangement Figure 4.10c , all the feed enters j the HP column. When the feed, is rich in the less volatile component, this arrangement produces a pure bottom stream and an impure Icistillate stream as shown in Figure 4.10c. The impure overhead i stream is further separated into a distillate stream ar.c a second bottom stream. when the feed is rich in the more volatile...

Xha

1 Floating pressure strategy or control is a technique pioneered by I Shir.skey 4,5 in which the column is trimmed or controlled to operate at the minimum possible pressure. This technique achieves significant energy savings during periods of favorable ambient i conditions. For most systems, relative volatility increases as pressure is i reduced, making separations easier the ensuing reduction in reflux ratio accounts for a lower reboiler duty as pressure reduces. This lower duty benefit is...

Cox Vapor Pressure Charts

Cox Chart Vapor Pressure

The most important term in both K values and the relative volatility j equation is the vapor pressure term. EFFECT OF TEMPERATURE This effect can be illustrated with the aid of j a Cox chart Figure 1.5, Reference 8 . This chart shows a steep increase of vapor pressure with temperature. For this reason, the K 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...

Ypq

Rasmusser. and M.L. Michelsen, Paper presented at the A.I.Ch.E. 87th National Meeting, 3oston, Ma., August, 1979. I 19. Soave, G.S., I.Chem. E. Syrap. Ser. 56_, p. 1.2 1, London, 1979. 20. Peng. D.Y. and D.B. Robinson, Ind. Eng. Chem. Fund., 15, 59 1976. 21. Benedict, M., G.B. Webb and L.C. Rubin, Chem. Enc. Prog., 47 3 , 419, 1951. 22. Orye, R.V., Ind. Eng. Chem. Proc. Des. Dev., 8, 579, 1969. 23. Starling, K.E., Hydroc. Proc., 5 3 , 101, 1971. 24. Edmister, W.C., and...

Kvalue Calculation

1.2.L rLa.ssificaticn of Prediction Methods K-Value prediction methods are often classified into hydrocarbon-type methods and chemical-type methods 10,11 . In hydrocarbon-type systems, effects of molecular interactions are relatively small, because the nature of the components is similar. On the other hand, it is most important to obtain good correlation at varying temperature and pressure, since many separations are carried out at high pressures. The approach used in hydrocarbon-type systems...

Estimating vaporliquid equilibria with UNIFAC

When experimental vapor-liquid equilibrium data are not available, you may be able to estimate them via the UNIFAC method. Gus K. Georgeton and Jude T. Sommerfeld, Georgia Institute of Technology Q Chemical engineers use vapor-liquid equilibrium VLE data in designing many types of separation processes and equipment. Experimental VLE data are of course the best, but when such data are not available the engineer has to make a choice run an experiment, or try an estimation method. This article...

Henry Kister Seminar

KISTER BROWN amp ROOT BRAUN, ALHAMBRA, CALIFORNIA COPYRIGHT BY H. Z. KISTER, MAY 26, 1983 No part of this publication may be reproduced without prior permission. The opinions expressed at this program are those of the seminar leader and not necessarily McGraw-Hill's. The seminar leader makes no representation, warranties or guarantees expressed or implied, as to the application or fitness of the ideas, suggestions, or recommendations, presented herein or during seminar discussions, for...

I

1.2.2 Hand Calculation Methods for Hydrocarbon-Type Systems K CHARTS Several charts giving K-values for hydrocarbons are available in tiie literature. Perhaps the easiest to use are the De Priester charts 47 , shown in Figure 1.11. These charts are a simplification of the Kellogg Charts 49 , and include experimental data not coverred by the Kellogg Charts. The Kellogg Charts 40 , and therefore the De Priester Charts 47 , are based on the Benedict-Webb-Rubin equation Section 1.2.3 . Edmister and...